Rook, a chessman taking knight for position (7)
I believe the answer is:
ranking
'position' is the definition.
(ranking is a kind of position)
'rook a chessman taking knight' is the wordplay.
'rook' becomes 'r' (abbreviation in chess).
'chessman' becomes 'king' (king is a kind of chessman**).
'taking' means one lot of letters goes inside another.
'knight' becomes 'n' (chess).
'a'+'king'='aking'
'aking' going around 'n' is 'anking'.
'r'+'anking'='RANKING'
'for' acts as a link.
(Other definitions for ranking that I've seen before include "Status" , "Position in a hierarchy" , "Classification" , "Place among seeds" , "Assigning a position to" .)