To be indisposed to hold money is smart (5)
I believe the answer is:
'is smart' is the definition.
(I've seen this before)
'to be indisposed to hold money' is the wordplay.
'to be indisposed' becomes 'sick' ('sick' can be similar in meaning to 'indisposed').
'to hold' is an insertion indicator.
'money' becomes 'l' (L can mean 'pounds').
'sick' enclosing 'l' is 'SLICK'.
(Other definitions for slick that I've seen before include "Film of spilled oil" , "it's very oily" , "Smooth" , "Smart" , "polished performance" .)