Plunder a grave perhaps (6)
I believe the answer is:
ravage
'plunder' is the definition.
(I've seen this before)
'a grave perhaps' is the wordplay.
'perhaps' is an anagram indicator.
'a'+'grave'='agrave'
'agrave' is an anagram of 'RAVAGE'.
(Other definitions for ravage that I've seen before include "Devastate, damage extensively" , "Sack" , "Cause extensive destruction" , "Devastation" , "Act like a 6" .)