Just a little bit catty? (4)
I believe the answer is:
atom
'bit catty?' is the definition.
'atom' can be an answer for 'bit' (I have seen 'Tiny bit' mean 'atom' so perhaps 'bit' could also mean 'atom'). I am unsure of the 'catty?' bit.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for atom that I've seen before include "Tiny particle, causes mighty explosion" , "Smallest amount" , "A mighty particle, can be explosive" , "A tiny particle of matter with a big bang" , "Bit of make-up" .)