Member hiding money in book (4)
I believe the answer is:
tome
'book' is the definition.
(a tome is a book)
'member hiding money' is the wordplay.
'member' becomes 'toe' (toe is a kind of member).
'hiding' is an insertion indicator.
'money' becomes 'm' (abbreviation in economics).
'toe' placed around 'm' is 'TOME'.
'in' is the link.
(Other definitions for tome that I've seen before include "War and Peace, say" , "Large and scholarly book" , "Large, weighty book" , "Large heavy book" , "Hefty volume" .)