Goes wild (4,4)
'goes wild' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for runs amok that I've seen before include "Loses control" , "Goes crazy" , "Attacks people violently and without discrimination" , "riots" .)
(Other definitions for revels that I've seen before include "Carousals, high jinks" , "Noisy celebrations" , "Our . . . . . . now are ended (The Tempest)" , "Noisy festivities" , "Has great fun with levers" .)