Black type of rook (4)
I believe the answer is:
bilk
'rook' is the definition.
(I've seen this in another clue)
'black type' is the wordplay.
'black' becomes 'b' (abbreviation as in pencil hardness).
'type' becomes 'ilk' (ilk can mean a type or kind).
'b'+'ilk'='BILK'
'of' is the link.
(Other definitions for bilk that I've seen before include "Defraud; Acker --, clarinettist" , "Thwart" , "Bamboozle" , "fleece" , "Cheat (of payment)" .)