Retribution seems in fashion (7)
I believe the answer is:
nemesis
'retribution' is the definition.
(thesaurus)
'seems in fashion' is the wordplay.
'fashion' is an anagram indicator.
'seems'+'in'='seemsin'
'seemsin' with letters rearranged gives 'NEMESIS'.
(Other definitions for nemesis that I've seen before include "Agent of (someone's) downfall" , "Archenemy" , "opponent you can't beat" , "Greek goddess - opponent who cannot be beaten" , "Come-uppance" .)