Wool supplier hiding blemish books clothing course (9)
I believe the answer is:
newmarket
'course' is the definition.
(I've seen this before)
'wool supplier hiding blemish books clothing' is the wordplay.
'wool supplier' becomes 'ewe' (a ewe is a female sheep).
'hiding' means one lot of letters goes inside another.
'blemish' becomes 'mark' (marking is a kind of blemishing).
'books' becomes 'NT' (abbreviation for New Testament).
'clothing' means one lot of letters goes inside another (some letters cover up or clothe others).
'ewe' going around 'mark' is 'ewmarke'.
'ewmarke' placed inside 'nt' is 'NEWMARKET'.
(Other definitions for newmarket that I've seen before include "Racing town" , "Racecourse - card game" , "horse-racing centre" , "Suffolk town" , "Suffolk racecourse" .)