Act without restraint on the European tour (3,3)
I believe the answer is:
let rip
'act without restraint' is the definition.
(I've seen this before)
'on the european tour' is the wordplay.
'on' means one lot of letters go next to another.
'the european' becomes 'le'.
'tour' becomes 'trip' (I've seen this in other clues).
'le' put next to 'trip' is 'LET RIP'.
(Other definitions for let rip that I've seen before include "Proceed unrestrained" , "Sound off" , "Act violently" , "Hasten" , "Speak without restraint" .)