Money is a bait that catches many (5)
I believe the answer is:
lucre
'money' is the definition.
(I know that lucre is a type of money)
'bait that catches many' is the wordplay.
'bait' becomes 'lure' (synonyms).
'that catches' means one lot of letters goes inside another.
'many' becomes 'c' (C is the Roman numeral for 100).
'lure' going around 'c' is 'LUCRE'.
'is a' is the link.
(Other definitions for lucre that I've seen before include "Possession of the rich" , "Ulcer (anag)" , "ill-gotten gain" , "(Dishonourably gained) money (poetic, literary)" , "(Filthy) profit" .)