Appropriate, top walls in gold (6)
I believe the answer is:
borrow
'appropriate' is the definition.
(thesaurus)
'top walls in gold' is the wordplay.
'top' becomes 'brow' (brow is a kind of top**).
'walls in' means one lot of letters goes inside another (I've seen this in other clues).
'gold' becomes 'or' ('or' is the heraldic name for gold).
'brow' placed around 'or' is 'BORROW'.
(Other definitions for borrow that I've seen before include "Take, use and return" , "Take on loan" , "Make use of library" , "In library, ask for" , "George ---, author; plagiarise" .)