Voice part in orchestral tour (4)
I believe the answer is:
alto
'voice part' is the definition.
(I've seen this in another clue)
'in orchestral tour' is the wordplay.
'in' says the answer is hidden in the clue.
'ALTO' is hidden within 'orchestral tour'.
(Other definitions for alto that I've seen before include "A singing voice or pitch" , "Member of choir" , "One who sings" , "Second of four parts (in singing)" , "Singing range" .)