Chess piece, not king, that's black in comparison (5)
I believe the answer is:
night
'black in comparison' is the definition.
'night' can be an answer for 'black' (night can mean as black as night). I am not certain of the 'in comparison' bit.
'chess piece not king' is the wordplay.
'chess piece' becomes 'knight' (knight is a type of chess piece).
'not' suggests deleting specific letters.
'king' becomes 'K' (chess abbreviation).
'knight' with 'k' taken away is 'NIGHT'.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for night that I've seen before include "What proverbially follows day" , "See 1 Across" , "Saturday -- Fever (film)" , "''Tender is the ...'' (F Scott Fitzgerald)|" , "Thing (anag)" .)