Occasionally stroke little piggy (3)
I believe the answer is:
toe
'little piggy' is the definition.
('this little piggy went to market' nursery rhyme)
'occasionally stroke' is the wordplay.
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
The alternating letters of 'stroke' are 'TOE'.
(Other definitions for toe that I've seen before include "Pedal digit" , "End of sock" , "Extremity of the body" , "Front of shoe" , "Lower end or tip" .)