Allows man to grab end of waist (4)
I believe the answer is:
lets
'allows' is the definition.
('let' can be a synonym of 'allow')
'man to grab end of waist' is the wordplay.
'man' becomes 'les' (**).
'to grab' is an insertion indicator.
'end of' indicates one should take the final letters.
The final letter of 'waist' is 't'.
'les' enclosing 't' is 'LETS'.
(Other definitions for lets that I've seen before include "Yes" , "we shall serve them again!" , "Allows or causes to" , "Leases" , "Permits" .)