Alternative article in gold (5)
I believe the answer is:
other
'alternative' is the definition.
(I've seen this before)
'article in gold' is the wordplay.
'article' becomes 'the' (the 'definite article' part of speech).
'in' indicates putting letters inside.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'the' inserted into 'or' is 'OTHER'.
(Other definitions for other that I've seen before include "Different, not the same one or this one" , "else!" , "Remaining" , "Second" , "Alternative - unrelated" .)