Having a go at taking cat out (9)
I believe the answer is:
attacking
'having a go at' is the definition.
'taking cat out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'taking'+'cat'='takingcat'
'takingcat' with letters rearranged gives 'ATTACKING'.
(Other definitions for attacking that I've seen before include "Assailing" , "Assaulting" , "offensive" .)