Relaxed, Peter and I, out for a spin (9)
I believe the answer is:
pirouette
'for a spin' is the definition.
(pirouette is a kind of spin)
'relaxed peter and i out' is the wordplay.
'relaxed' is an anagram indicator.
'and' says to put letters next to each other.
'i'+'out'='iout'
'peter' after 'iout' is 'ioutpeter'.
'ioutpeter' with letters rearranged gives 'PIROUETTE'.
(Other definitions for pirouette that I've seen before include "Balletic whirl" , "Take turn on foot" , "Spin on one foot" , "bit of dancing" , "A dancer's spinning movement on tiptoe" .)