Fur, special fit (5)
I believe the answer is:
sable
'fur' is the definition.
(sable is a kind of fur)
'special fit' is the wordplay.
'special' becomes 'S' (common abbreviation as in Special Air Service).
'fit' becomes 'able' (similar in meaning).
's'+'able'='SABLE'
(Other definitions for sable that I've seen before include "Brush" , "North Asian marten" , "Bales of expensive Russian fur" , "Adventurous courage" , "Black; antelope" .)