Rock, for instance, keeps wicket (4)
I believe the answer is:
sway
'rock' is the definition.
('sway' can be a synonym of 'rock')
'for instance keeps wicket' is the wordplay.
'for instance' becomes 'say'.
'keeps' indicates putting letters inside.
'wicket' becomes 'w'.
'say' going around 'w' is 'SWAY'.
(Other definitions for sway that I've seen before include "Move from side to side; influence" , "Swing from side to side, or influence opinion" , "Vacillate" , "Strong influence" , "Rock, stagger" .)