If corrupt, do anticipate severe punishment (12)
I believe the answer is:
decapitation
'severe punishment' is the definition.
'if corrupt do anticipate' is the wordplay.
'if corrupt' is an anagram indicator.
'do'+'anticipate'='doanticipate'
'doanticipate' is an anagram of 'DECAPITATION'.
(Other definitions for decapitation that I've seen before include "ultimate downfall?" , "Beheading" , "Fate of Anne Boleyn" .)