Livery company attached to corporation in Kent area (7)
I believe the answer is:
costume
'livery' is the definition.
(thesaurus)
'company attached to corporation in kent area' is the wordplay.
'company' becomes 'co' (abbreviation).
'attached to' is a charade indicator (letters next to each other).
'corporation' becomes 'tum' ('corporation' can humorously mean belly fat).
'in' indicates putting letters inside.
'kent area' becomes 'se'.
'tum' going inside 'se' is 'stume'.
'co'+'stume'='COSTUME'
(Other definitions for costume that I've seen before include "Clothes for a play or fancy dress ball" , "(Historic etc) dress" , "Outfit" , "Clothing" , "Duds" .)