Closing gap, don't stop thug (4)
I believe the answer is:
goon
'thug' is the definition.
(synonyms)
'closing gap don't stop' is the wordplay.
I cannot really understand how this works, but
'stop' could be 'go' (going is a kind of stopping) and 'go' is present in the answer.
The remaining letters 'on' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for goon that I've seen before include "SPIKE] ?" , "person making fool of himself" , "Is this show" , "Stupid person" , "Hired thug" .)