Tell raver off -- one's experiencing a trip (9)
I believe the answer is:
traveller
'one's experiencing a trip' is the definition.
(someone going on a trip)
'tell raver off' is the wordplay.
'off' indicates an anagram.
'tell'+'raver'='tellraver'
'tellraver' anagrammed gives 'TRAVELLER'.
(Other definitions for traveller that I've seen before include "Salesman" , "One on the move" , "Jet-setter" , "Representative" , "Voyager" .)