Position of Queen, a piece capturing knight (7)
I believe the answer is:
ranking
'position' is the definition.
(ranking is a kind of position)
'queen a piece capturing knight' is the wordplay.
'queen' becomes 'r' (r is abbreviation regina. e.g. in ER ).
'piece' becomes 'king' (king is a kind of piece**).
'capturing' means one lot of letters goes inside another.
'knight' becomes 'n' (chess).
'a'+'king'='aking'
'aking' enclosing 'n' is 'anking'.
'r'+'anking'='RANKING'
'of' is the link.
(Other definitions for ranking that I've seen before include "Place among seeds" , "Classification" , "Grading" , "position on graded scale" , "Position in a hierarchy" .)