Continue to be someone foolish (4)
I believe the answer is:
goon
'someone foolish' is the definition.
I can't judge whether this definition defines the answer.
'continue to be' is the wordplay.
'continue' becomes 'on' (I've seen this in other clues).
'to' says to put letters next to each other (I've seen this in other clues).
'be' becomes 'go' (going is a kind of being).
'on' after 'go' is 'GOON'.
(Other definitions for goon that I've seen before include "Foolish person - thug (US)" , "Silly person - bully (US)" , "SPIKE] ?" , "Is this show" , "Sellers for example" .)