Little dog eating male's shoe (4)
I believe the answer is:
pump
'shoe' is the definition.
(pump is a kind of shoe)
'little dog eating male's' is the wordplay.
'little dog' becomes 'pup' (**).
'eating' is an insertion indicator.
'male' becomes 'm' (common abbreviation).
'pup' going around 'm' is 'PUMP'.
(Other definitions for pump that I've seen before include "The heart is one" , "Flat shoe; siphon" , "Device to move fluid or gas by pressure or suction" , "Compressor, light shoe" , "Device for moving liquids by force or suction" .)