Continue as thug (4)
I believe the answer is:
goon
'thug' is the definition.
(synonyms)
'continue' is the wordplay.
I cannot quite understand how this works, but
'continue' could be 'on' (I've seen this in other clues) and 'on' is found within the answer.
The remaining letters 'go' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
'as' acts as a link.
Can you help me to learn more?
(Other definitions for goon that I've seen before include "Stupid person" , "He's very stupid" , "person making fool of himself" , "Silly person - bully (US)" , "Foolish person - thug (US)" .)