Husband-to-be receives note: it's money (7)
I believe the answer is:
finance
'it's money' is the definition.
(finance is the management of money)
'husband-to-be receives note' is the wordplay.
'husband-to-be' becomes 'fiance' (I've seen this in another clue).
'receives' means one lot of letters goes inside another (inserted letters are received).
'note' becomes 'n' (abbreviation).
'fiance' placed around 'n' is 'FINANCE'.
(Other definitions for finance that I've seen before include "Money affairs" , "funding" , "Money matters" , "Fund" , "Back" .)