Livelong for a Gold brooch (5)
I believe the answer is:
orpin
'livelong' is the definition.
(synonyms)
'a gold brooch' is the wordplay.
'a gold' becomes 'or' ('or' is the heraldic name for gold).
'brooch' becomes 'pin' (I've seen this before).
'or'+'pin'='ORPIN'
'for' is the link.
(Other definitions for orpin that I've seen before include "Purple, broad-leafed stonecrop" , "Bloomer" , "Variety of stonecrop" , "Stonecrop that's purple" , "Plant" .)