Witty remark about us with long whiskers (9)
I believe the answer is:
moustache
'whiskers' is the definition.
(moustache is a kind of whiskers)
'witty remark about us with long' is the wordplay.
'witty remark' becomes 'mot' (I've seen this before).
'about' means one lot of letters goes inside another.
'with' is a charade indicator (letters next to each other).
'long' becomes 'ache' (to long for something is to ache for it).
'mot' placed around 'us' is 'moust'.
'moust'+'ache'='MOUSTACHE'
(Other definitions for moustache that I've seen before include "something hairy" , "See 1" , "Facial hair on a man" , "Hair on upper lip" , "Facial hair touches Ma" .)