1 POPISH PLOT Hoax to discredit catholics
Even if your knowledge of late 17th century religious conflict is not as sharp as it might be, I thnk this is gettable both from the "Catholic hoax" and the wordplay. Titus Oates was the character at the centre of the piece, a serial liar who invented a plot by the Jesuits to assassinate Charles II and whipped up considerable anti catholic hysteria until (sort of) exposed as a perjuror, by which time at least 22 innocent high-ranking Catholics had been executed. To get a modern day flavour, try looking up "Tom Watson" in conjunction with, say, "Ted Heath".* Ah yes, the wordplay. "Try" is POP, as in have a pop at, "rats" is PISH by loose association of mild expletive (I'm open to better suggestions). Wrap one round the other, and add LOT for "many"
*Other suggestions are welcome: lets have some conspiracy fun!
6 OBEY Conform
Being overweight is OBEsitY. As instructed strike "sit" out.
9 SEASIDE Coast
No fancy geographical term required. If you exclude southeast, not only do you miss out on Margate, but you set SE ASIDE
10 MOSELLE German wine
Endless champagne is MOË(t), insert SELL for trade. Other fizzy drinks are available.
12 HEART mood (I think)
By one of those three point turns in a Thesaurus, mood via disposition gets to heart. The wordplay invites you to imagine a similar if reversed solicism to thou is as HE ART. Don't shoot your humble messenger.
13 UNSPOILED pristine
Re-sort ENDS UP and throw in a slick of OIL.
14 SPRINGER SPANIEL dog
An extended talk is a SPIEL. Put it about RINGERS for callers, and PAN for slag off.
17 EVENING STANDARD (news) paper
The London version manages to prove that you don't have to charge your readers after all (copy to our beloved News UK, please). Quality gives rise to STANDARD, and becoming less erratic is EVENING (out). Yodafy
20 COMBATIVE militant
Search: COMB. In operation without C(aught) gives A(c)TIVE
21 TOXIC damaging
Steer in this incarnation is OX, around which the uncontrolled TIC settles.
23 ANTWERP European port
Take the letters of WEPT and RAN, "off" them and see how they settle.
Today's hidden, in yakitORI NO COmment.
25 PUCE Colour
Take the lightest stone you know, PUmiCE, and strike M(arks) and I.
26 LEMON GRASS fragrant ingredient
Looks like an anagram, and is, of ROAMS GLENS. Smells like this █████ (scratch here)
1 POST-HASTE very quickly
Our Setter eschews Spooner, but invites us to take HOST entertainer and PASTE fake gems, and switch the first letters, tops in down clues
2 PLAZA public space
Arizona's abbrev. is AZ, and after overturning it and a mountain ALP, it provides our answer
3 SPITTING IMAGE Duplicate
A carefree symbol for slightly damp weather would of course be, well, our answer. Wouldn't it have been a more fun clue as, say → ?
4 PRELUDE passage that opens
Bar is PREcLUDE. Remove the C(lubs)
5 OSMOSIS Absorption.
IS under cOSMOS or universe without the first letter. Curiously the third clue to require you to remove a C
7 BALALAIKA Russian instrument
An Albanian is a BALKAn, most of which gathers round "in the style of" À LA plus I, one
8 YIELD &lit...
...I think. If you take a variable, Y and use it to replace the F of FIELD (arable land), you get an answer that, if you squint a bit, is also clued by the surface meanng.
11 STOP AT NOTHING Be determined...
...and what you do if you complete a countdown. Mind you, some of us can remember the countdown to acquisition of signal from the returning Apollo 13 extending for a terrifying 87 seconds beyond Zero, and the explosion of relief when the silence broke.
15 RHEUMATIC to do with joint complaints
A write in for me (my sister had teenage rheumatic fever, very nasty), but it's an anagram of IRATE MUCH
16 LUDICROUS Laughable.
Follow the construction manual carefully. Begin with piece 1, L(earner). Add piece 2 and 3, STUDIOUS (bookish). Remove the temporary piece 2, ST(umped). Insert piece 4, CR(redit) where you can make it fit. I appear to be suffering from grandchild-induced LegOCD
18 GLIMPSE Quick butcher's ('ook)
CRS. I rather appreciated this construction. Good just gives the G. Easy gives SIMPLE, in which you swap the L(arge) and the S(mall).
19 TREMOLO fluttering effect
Usually as heard on a pipe organ when rapidly changing the airflow in mawkish Victorian sentimental pieces. Activity under lids, R(apid) E(ye) M(ovement) is kept by TO and LO (behold)
20 CHAMP &lit
More succesful to my eye than the other one. Fellow, CHAP, accepts the first letter of Medals.
22 XHOSA South African
Strictly speaking, there should be a click sound at the beginning, but we have no space or symbol. Anagram of HAS OX