Rant's companion (4)
I believe the answer is:
rave
'rant's companion' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rave that I've seen before include "Fume" , "Modern youth dance - sounds hysterical" , "Enthusiastically favourable review" , "Rant - noisy, all-night party" , "Rapturous" .)