Forked out about fifty for tartan (5)
I believe the answer is:
plaid
'tartan' is the definition.
(synonyms)
'forked out about fifty' is the wordplay.
'forked out' becomes 'paid' (I've seen this before).
'about' indicates putting letters inside.
'fifty' becomes 'l' (Roman numeral).
'paid' enclosing 'l' is 'PLAID'.
'for' acts as a link.
(Other definitions for plaid that I've seen before include "woollen cloth" , "Tartan patterned cloth" , "Part of Scots dress or Welsh party" , "Cloth for a Highlander" , "material" .)