Classy uniform, rating's favourite clothing (8)
I believe the answer is:
upmarket
'classy' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I don't see?
'uniform rating's favourite clothing' is the wordplay.
'uniform' becomes 'U' (phonetic alphabet: alpha, bravo, charlie etc.).
'rating' becomes 'mark' (mark is a kind of rating).
'favourite' becomes 'pet' (synonyms).
'clothing' is an insertion indicator (some letters cover up or clothe others).
'mark' placed into 'pet' is 'pmarket'.
'u'+'pmarket'='UPMARKET'
Can you help me to learn more?
(Other definitions for upmarket that I've seen before include "for wealthy consumers" , "For the better off" , "Superior" , "high quality" , "Relatively expensive" .)