Insufficient money for cake (10)
I believe the answer is:
shortbread
'cake' is the definition.
(shortbread is a kind of cake)
'insufficient money' is the wordplay.
'insufficient' becomes 'short' ('short' can be similar in meaning to 'insufficient').
'money' becomes 'bread' (bread is a kind of money).
'short'+'bread'='SHORTBREAD'
'for' is the link.
(Other definitions for shortbread that I've seen before include "Crumbly biscuit rich in butter" , "Brittle buttery cake" , "Biscuit with plenty of butter" , "sweet but easily crumbling" , "biscuits" .)