Persist in being a silly person (4)
I believe the answer is:
goon
'silly person' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for goon that I've seen before include "SPIKE] ?" , "someone rather stupid" , "person making fool of himself" , "Stupid person" , "Foolish person - thug (US)" .)