Kitty chasing second little bit (4)
I believe the answer is:
spot
'little bit' is the definition.
(thesaurus)
'kitty chasing second' is the wordplay.
'kitty' becomes 'pot' ('pot' can be a synonym of 'kitty').
'chasing' is a charade indicator (letters next to each other).
'second' becomes 's' (common abbreviation).
'pot' after 's' is 'SPOT'.
(Other definitions for spot that I've seen before include "Catch sight of - pimple" , "Observe - place" , "make out" , "Detect" , "Small mark; observe" .)