Squealed "yes" and assisted cockney (6)
I believe the answer is:
yelped
'squealed' is the definition.
(I've seen this in another clue)
'yes and assisted cockney' is the wordplay.
'yes' becomes 'y'.
'and' is a charade indicator (letters next to each other).
'assisted cockney' becomes ''elped' ('helped' - 'help' can be a synonym of 'assist' - said with a cockney accent, dropping the 'H').
'y'+'elped'='YELPED'
(Other definitions for yelped that I've seen before include "Uttered sharp barks" , "Uttered short cry like a dog" , "Made sharp shrill bark of dog" , "Barked" , "Made shrill sound as of dog" .)