Functional uniform with fur (6)
I believe the answer is:
usable
'functional' is the definition.
(having a use)
'uniform with fur' is the wordplay.
'uniform' becomes 'U' (phonetic alphabet: alpha, bravo, charlie etc.).
'with' is a charade indicator (letters next to each other).
'fur' becomes 'sable' (sable is a kind of fur).
'u'+'sable'='USABLE'
(Other definitions for usable that I've seen before include "Functional, operational" , "Not vain, presumably" , "Fit for employment" , "Fit for service" , "Of potential utility" .)