Bound to accept gift put up as pledge (7)
I believe the answer is:
deposit
'pledge' is the definition.
(I know that deposit is a type of guarantee)
'bound to accept gift put up' is the wordplay.
'bound' becomes 'tied' (similar in meaning).
'to accept' means one lot of letters goes inside another.
'gift' becomes 'sop' (sop can mean a gift or bribe).
'put up' is a reversal indicator.
'tied' enclosing 'sop' is 'tisoped'.
'tisoped' reversed gives 'DEPOSIT'.
'as' is the link.
(Other definitions for deposit that I've seen before include "secure an item" , "Sum of money paid into a bank account" , "Money in bank - part payment" , "Set down" , "Layer laid down" .)