First-class beer brought up in splendid clothing (7)
I believe the answer is:
regalia
'splendid clothing' is the definition.
'regalia' can be an answer for 'clothing' (regalia is a kind of clothing). I'm not sure about the 'splendid' bit.
'first-class beer brought up' is the wordplay.
'first class' becomes 'ai' (A1 - top quality).
'beer' becomes 'lager' (type of beer).
'brought up' says the letters should be written backwards (in a down clue, letters go up).
'ai'+'lager'='ailager'
'ailager' in reverse letter order is 'REGALIA'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for regalia that I've seen before include "Emblems of royalty used at coronations" , "Orb and sceptre etc" , "Orb and sceptre, for example" , "Finery" , "Algeria (anag)" .)