Steak and kidney, perhaps: regularly chew a slice (5)
I believe the answer is:
piece
'a slice' is the definition.
(I know that slice can be written as piece)
'steak and kidney perhaps regularly chew' is the wordplay.
'steak and kidney perhaps' becomes 'pie' (steak and kidney is a type of pie).
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'chew' are 'ce'.
'pie'+'ce'='PIECE'
(Other definitions for piece that I've seen before include "knight, perhaps" , "King, perhaps" , "wedge a > bit" , "Separate part of a whole" , "constituent" .)