Money making constant part of temptation (5)
I believe the answer is:
lucre
'money' is the definition.
(lucre is a kind of money)
'constant part of temptation' is the wordplay.
'constant' becomes 'c' (mathematical abbreviation).
'part of' indicates putting letters inside (part of the inside).
'temptation' becomes 'lure' (lure is a kind of temptation).
'c' put within 'lure' is 'LUCRE'.
'making' is the link.
(Other definitions for lucre that I've seen before include "(Filthy) profit" , "Ulcer (anag)" , "Sordid gain; riches" , "There's money" , "Money or wealth" .)