Gold French sea shell (5)
I believe the answer is:
ormer
'shell' is the definition.
(I've seen this before)
'gold french sea' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'french sea' becomes 'mer' ('sea' in French).
'or'+'mer'='ORMER'
(Other definitions for ormer that I've seen before include "Ear-shaped shell" , "Shellfish" , "Ear-shell" , "Delicacy from Channel Islands" , "Sea-ear, an abalone found near the Channel Is" .)