Silver, in heraldry (6)
I believe the answer is:
argent
'silver in heraldry' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for argent that I've seen before include "Silver on a coat of arms" , "(In heraldry) silver - garnet (anag)" , "White" , "Heraldic term for silver" , "Colour" .)