Declare some grave results (4)
I believe the answer is:
aver
'declare' is the definition.
(averring is a kind of declaring)
'some grave results' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'AVER' can be found hidden inside 'grave results'.
(Other definitions for aver that I've seen before include "being assertive" , "Declare or insist" , "State firmly - even rave about" , "State firmly, declare" , "Firmly maintain" .)