In rut or maybe act without restraint (3,4)
I believe the answer is:
run riot
'act without restraint' is the definition.
(I've seen this in another clue)
'in rut or maybe' is the wordplay.
'maybe' is an anagram indicator.
'in'+'rut'+'or'='inrutor'
'inrutor' is an anagram of 'RUN RIOT'.
(Other definitions for run riot that I've seen before include "Act wantonly, without restraint" , "Act wildly" , "Behave in uncontrolled way as mob might" , "go crazy" , "high-scoring test match" .)