Animal with dark head and whiskers (5)
I believe the answer is:
beard
'whiskers' is the definition.
(synonyms)
'animal with dark head' is the wordplay.
'animal' becomes 'bear' (bear is a kind of animal).
'with' is a charade indicator (letters next to each other).
'head' suggests taking the first letters.
The first letter of 'dark' is 'd'.
'bear'+'d'='BEARD'
'and' acts as a link.
(Other definitions for beard that I've seen before include "Facial hair" , "SECOND PART OF 14" , "Oppose with effrontery" , "In good health; very" , "hair extension" .)