Lacking money for a buttery biscuit (10)
I believe the answer is:
shortbread
'a buttery biscuit' is the definition.
(type of biscuit)
'lacking money' is the wordplay.
'lacking' becomes 'short' (to be short something is to lack it).
'money' becomes 'bread' (bread is slang for money).
'short'+'bread'='SHORTBREAD'
'for' acts as a link.
(Other definitions for shortbread that I've seen before include "Biscuit with plenty of butter" , "Crumbly biscuit rich in butter" , "Brittle buttery cake" , "biscuits" , "sweet but easily crumbling" .)