Advantage for us sporting baggy clothes (4,5)
I believe the answer is:
plus fours
'baggy clothes' is the definition.
(type of trousers)
'advantage for us sporting' is the wordplay.
'advantage' becomes 'plus' (I've seen this before).
'sporting' is an anagram indicator.
'for'+'us'='forus'
'forus' is an anagram of 'fours'.
'plus'+'fours'='PLUS-FOURS'
(Other definitions for plus fours that I've seen before include "Old golfwear" , "leisure wear" , "Surplus of golf knickerbockers" , "Sportswear" , "golfer's wear" .)