Fur bachelor found in auction (5)
I believe the answer is:
sable
'fur' is the definition.
(I know that sable is a fur)
'bachelor found in auction' is the wordplay.
'bachelor' becomes 'B' (abbreviation e.g. BA=Bachelor of Arts).
'found in' is an insertion indicator.
'auction' becomes 'sale' (I've seen this before).
'b' put within 'sale' is 'SABLE'.
(Other definitions for sable that I've seen before include "Fur from member of weasel family" , "Adventurous courage" , "North Asian marten" , "Bales (anag.)" , "Bales of rich fur" .)