Impose hand threateningly? Nothing in it (5)
I believe the answer is:
foist
'impose' is the definition.
(I know this)
'hand threateningly? nothing in it' is the wordplay.
'hand threateningly?' becomes 'fist' (hand in a fist for fighting).
'nothing' becomes 'O' (looks like zero - 0).
'in it' means one lot of letters goes inside another.
'fist' enclosing 'o' is 'FOIST'.
(Other definitions for foist that I've seen before include "palm off" , "Impose, inflict" , "Impose (upon)" , "To - something on a person is to impose it" , "Insinuate" .)