Regularly strokes digit (3)
I believe the answer is:
toe
'digit' is the definition.
(digit on a foot)
'regularly strokes' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternate letters of 'strokes' are 'TOE'.
(Other definitions for toe that I've seen before include "End of sock" , "one digit?" , "'Little piggy'" , "One of the lower digits" , "low digit" .)