Reviewed rank with chess piece on (7)
I believe the answer is:
working
'on' is the definition.
'reviewed rank with chess piece' is the wordplay.
'reviewed' says the letters should be written backwards.
'rank' becomes 'row' (I've seen this in another clue).
'with' says to put letters next to each other.
'chess piece' becomes 'king' (king is a kind of chess piece).
'row' backwards is 'wor'.
'wor'+'king'='WORKING'
(Other definitions for working that I've seen before include "Employed" , "Operating" .)