Solving Time: 28mins, longer than usual given the usual blogger's adrenalin rush, the SE corner in particular taking time to complete. I suspect this was a harder than average crossword, judging by the number of answers I have put in without properly understanding the wordplay.. let's hope writing the blog will provide some elucidation. Meantime, it seemed technically perfectly OK and has some very fine surface readings - I enjoyed it, a good effort, thank you setter

cd = cryptic definition, dd = double definition, rev = reversed, homophones are written in quotes, anagrams as (--)*

Across
1	goalpost - net = GOAL + POST = message, point being that it is unfair to move them
5	pampas - SAP MAP rev.
10	tango - many of us will be familiar with the NATO Alphabet, in which T tango is followed by U uniform. But how does "walk on beat" fit in? I'm missing something here. Is it just a waggish definition of dancing? no, simpler still, just beat = TAN + GO = walk. Thanks Jack, & MC>
11	omitted; ask if needed
12	skydivers - SKIVERS containing yard = YD
13	dry up - dd
14	emerald - ERA + LD containing ME
16	loiter - American volume = LITER is empty, ie has 0 in..
18	uppers - dd - uppers are psychoactive drugs, which the Times likes to include regularly in its crosswords. And if you are unlucky you could be on your uppers, ie unable to afford shoes with soles..
20	dustman - DUST MAN seems relevant advice to someone neglectful of housework. Why a boffin in particular needs to give it, I had no clue, but google was my friend and tells me that the Dickens novel Our Mutual Friend is properly titled "Our Mutual Friend, or the Golden Dustman," the dustman in question being named Noddy Boffin. Never did like Dickens
22	burst - chest = BUST containing R = right
23	orphanage - cd, point being that if you had them, you wouldn't be there
25	up-country - no explanation needed?
26	leapt - LEAP + T. I'm not certain of the precise construction of this clue, it has a slightly dodgy feel to it. But the answer is clear enough, so wotthehell
27	Tallis - TALL + IS, to make a composer, Thomas Tallis, that even I have heard of
28	thatcher - T(h)E + R(oof) containing HATCH
Down
1	go to seed - higher being = GOD containing TO SEE = to understand
2	annoy - (t)ANNOY
3	Proxima Centauri - PROM containing XI, + (CERTAIN)* containing AU = gold. My first in, and the nearest star to our own, a piddling 4.2 light years away.
4	suspend - S + US + P(risoner's) + END
6	A Study in Scarlet - redden, taken apart, = red den, a study in scarlet, geddit? The book in question being Conan Doyle's first Holmes book. Why have we such a fixation with violent death?
7	pachyderm - (CHAMP RE(a)DY)*
8	steppe - STEE(p) containing PP = pages
9	teasel - (la)TE AS EL(even)
15	empirical - (MIRACLE)* containing PI = good. A very neatly constructed clue, I thought
17	investor - half dressed = IN VEST + the other sort of gold, OR. An angel being a luvvies' term for a theatrical investor
19	snooty - puppet = SOOTY containing N for North pole. I see Sooty as the complete answer to those who claim that children's TV used to be better than it is today. It makes Teletubbies seem like Newsnight, in comparison.
20	diptych - get low = DIP, + TYCH, sounds like tick. A double painting, often early and religious in nature
21	abduct - A DUCT containing B = book.
24	abash - the final one I failed to understand, but I now see it is AB = tar in the maritime sense, + ASH = tree