Run too wild when travelling (2,4)
I believe the answer is:
on tour
'travelling' is the definition.
(on tour is a kind of travelling)
'run too wild' is the wordplay.
'wild' is an anagram indicator.
'run'+'too'='runtoo'
'runtoo' with letters rearranged gives 'ON TOUR'.
'when' acts as a link.
(Other definitions for on tour that I've seen before include "Going from place to place" , "No rout (anag.)" , "Travelling about" , "Doing a round of performances (of actor, band etc)" .)