Rating about empty election bombshell (7)
I believe the answer is:
grenade
'bombshell' is the definition.
(I know that grenade is a type of bombshell)
'rating about empty election' is the wordplay.
'rating' becomes 'grade' (grade is a kind of rating).
'about' is an insertion indicator.
'empty' suggests removing the centre.
'election' with its centre taken out is 'en'.
'grade' enclosing 'en' is 'GRENADE'.
(Other definitions for grenade that I've seen before include "Angered (anag)" , "Hand-thrown bomb" , "Small hand missile" , "Bomb with a pin" , "Small bomb thrown by hand" .)