Exhibit gaping hole with little width inside (4)
I believe the answer is:
'exhibit gaping' is the definition.
(to gawp is exhibit a gaping mouth)
'hole with little width inside' is the wordplay.
'hole with' becomes 'gap' (I am not sure about the 'with' bit.).
'little' says to take the initial letters.
'inside' is an insertion indicator.
The initial letter of 'width' is 'w'.
'gap' going around 'w' is 'GAWP'.
(Other definitions for gawp that I've seen before include "Watch open-mouthed" , "Stare idiotically" , "Stare stupidly" , "Look stupid(ly)" , "Stare open-mouthed" .)