John turned up grasping and savage (6)
I believe the answer is:
vandal
'savage' is the definition.
(I know that Vandal is a type of savage)
'john turned up grasping and' is the wordplay.
'john' becomes 'lav' (both can mean a toilet).
'turned up' says the letters should be written in reverse.
'grasping' is an insertion indicator (inserted letters are held or grasped).
'lav' reversed gives 'val'.
'val' placed around 'and' is 'VANDAL'.
(Other definitions for vandal that I've seen before include "Defacer or wrecker" , "One who causes wilful damage to property" , "Cultural destroyer" , "Destroyer or defacer of property" , "Person causing wanton damage" .)