Fight cat off American slave (9)
I believe the answer is:
spartacus
'slave' is the definition.
(escaped slave)
'fight cat off american' is the wordplay.
'fight' becomes 'spar' (sparring is a kind of fighting).
'off' is an anagram indicator.
'american' becomes 'US' (abbreviation for United States).
'cat' is an anagram of 'tac'.
'spar'+'tac'+'us'='SPARTACUS'
(Other definitions for spartacus that I've seen before include "Leader of the slave revolt against Rome, 73BC" , "Roman gladiator who led slaves in revolt" , "Thracian who led the 73 BC slave revolt against Rome" , "1960 gladiator film" , "Roman revolutionary" .)