Like a cat, black and suffering from fleas? (6)
I believe the answer is:
bitchy
'like a cat' is the definition.
(catty can mean bitchy)
'black and suffering from fleas?' is the wordplay.
'black' becomes 'b' (as in pencil classifications).
'and' is a charade indicator (letters next to each other).
'suffering from fleas?' becomes 'itchy' (an animal suffering from fleas might itch).
'b'+'itchy'='BITCHY'
(Other definitions for bitchy that I've seen before include "malicious" , "Unpleasant and spiteful like female dog" , "Speaking spitefully in manner of female canine" , "Catty" .)