Degenerate spilt reps ale (7)
I believe the answer is:
relapse
'degenerate' is the definition.
(to relapse is to degenerate or regress)
'spilt reps ale' is the wordplay.
'spilt' indicates anagramming the letters.
'reps'+'ale'='repsale'
'repsale' is an anagram of 'RELAPSE'.
(Other definitions for relapse that I've seen before include "Fall back into former state" , "Fall back into old ways" , "Deterioration after period of improvement" , "Degenerate like pleaser" , "Fail to maintain progress" .)