Piece of chivalry (6)
I believe the answer is:
knight
'piece of chivalry' is the definition.
'knight' can be an answer for 'piece' (chess piece). I'm not sure about the 'of chivalry' bit.
'piece of chivalry' is the wordplay.
'piece' becomes 'k' (abbreviation for King).
'of chivalry' becomes 'night' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'k'+'night'='KNIGHT'
Can you help me to learn more?
(Other definitions for knight that I've seen before include "Gawain?" , "Titled man - chessman" , "Holder of non-hereditary title in UK" , "Give title of 'Sir' to" , "Chess piece or non-hereditary English peer" .)