Solving time : 14 minutes - on the fast side for me, so I suspect there will be some very slick times out there. I was held up in the hippy corner by two unfamiliar words that eventually came from wordplay. It appeared to me there were rather a lot of letter subtraction clues in here, and some pretty nice long anagrams. And away we go...

Across
1	BACK(=champion),STRAIGHT(=clear). Wasn't sure if this was the racecourse or the tie, took the checking H from 6d to see this
9	(d)OWNER: the first of our subtractions today
10	E(as)TERN,ALLY: and the second
12	ESTATE: double definition
13	NUTRIENT: NUT, then I in RENT, got from definition before I saw wordplay
15	BOLERO: OLE(=approval) in BRO. A dance, a relentless piece of music and a horrific 80's movie
17	AD(=newspaper iterm),JUST(in Chambers - "quite, absolutely, indeed"): Not the usage of JUST that I am used to, but it works
20	RAN,KLE(=ELK backwards): Doe, a deer, a gnu or elk
21	STOCKPO(r)T: subtraction number 3
25	ANNU(a)L: The second article (take your pick if the first is AN or A), and fourth subtraction
26	STOVEPIPE HAT: (AT,PET,SHOP,IVE), fun little anagram
Down
1	BLOUSON: LOUS(y) in BON(=NOB<=). New word to me, and relieved to find that it means a loose outer garment gathered into a waistband
3	SYRIA: (AIRY,S)<= - I liked this reversal
4	(t)RIES,LING: more subtraction
5	IDEA: hidden in hIDE-And-seek
7	PLEASED AS PUNCH: (SPACE,HE,LANDS)
8	ZYDECO: booZY, then EC in DO, got this from the definition before sorting out the wordplay
14	INSOVLENT: V in INSOLENT
16	LAST-GASP: nice construction here - ST,GAS(=talk) in LAP
19	NOTELET: TELETHON without the H reversed
23	CRAMP: RAM in CP (from PicniC reversed)
25	KIE(l),V: Kiel being a German port