Fat female gundog (4)
I believe the answer is:
flab
'fat' is the definition.
(I know that flab is a type of fat)
'female gundog' is the wordplay.
'female' becomes 'f' (abbreviation).
'gundog' becomes 'lab' (labrador).
'f'+'lab'='FLAB'
(Other definitions for flab that I've seen before include "spare tyre?" , "Unwanted body fat" , "Excess body fat" , "Ugly, surplus flesh" , "Soft loose flesh" .)