Rotting corpse in plot (8)
I believe the answer is:
conspire
'plot' is the definition.
(conspiring is a kind of plotting)
'rotting corpse in' is the wordplay.
'rotting' is an anagram indicator.
'corpse'+'in'='corpsein'
'corpsein' is an anagram of 'CONSPIRE'.
(Other definitions for conspire that I've seen before include "implicated in plot" , "Act secretly with others" , "Collude" , "Secretly plan together" , "'Plot, connive (8)'" .)