Fur, black, entered in auction (5)
I believe the answer is:
sable
'fur' is the definition.
(sable is a kind of fur)
'black entered in auction' is the wordplay.
'black' becomes 'b' (as in pencil classifications).
'entered in' indicates putting letters inside.
'auction' becomes 'sale' (I've seen this before).
'b' placed inside 'sale' is 'SABLE'.
(Other definitions for sable that I've seen before include "Bales (anag.)" , "Marten's fur - dark black" , "Fur - heraldic black" , "Bales of valuable Russian fur" , "Literary black" .)