Declare rave over (4)
I believe the answer is:
aver
'declare' is the definition.
(averring is a kind of declaring)
'rave over' is the wordplay.
'over' indicates an anagram.
'rave' is an anagram of 'AVER'.
(Other definitions for aver that I've seen before include "possessions once" , "State firmly - don't rave" , "being assertive" , "State decisively" , "Declare or insist" .)