Fight back, man, and get tough! (7)
I believe the answer is:
spartan
'tough' is the definition.
(thesaurus)
'fight back man' is the wordplay.
'fight' becomes 'spar' (sparring is a kind of fighting).
'back' is a reversal indicator.
'man' becomes 'nat' ().
'nat' reversed gives 'tan'.
'spar'+'tan'='SPARTAN'
'and get' is the link.
(Other definitions for spartan that I've seen before include "Of conditions, harsh and lacking comforts" , "Not comfortable" , "Strictly disciplined" , "Lacking luxury, austere" , "Frugal" .)