Go wild (3,4)
I believe the answer is:
run riot
'go wild' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for run riot that I've seen before include "behave in unrestrained way" , "Of mob, throw off all restraint" , "Go berserk" , "high-scoring test match" , "Behave in uncontrolled way as mob might" .)