Proceed, twit! (4)
I believe the answer is:
goon
'proceed twit' is the definition.
I can't tell whether this defines the answer.
'proceed twit' is the wordplay.
'proceed' becomes 'go' ('go' can be a synonym of 'proceed').
'twit' becomes 'on' (I can't explain this - if you can you should give a lot more credence to this answer).
'go'+'on'='GOON'
Can you help me to learn more?
(Other definitions for goon that I've seen before include "He's very stupid" , "Is this show" , "Sellers for example" , "Stupid person" , "person making fool of himself" .)