Original new musical heading to West End (6)
I believe the answer is:
native
'original' is the definition.
(native can mean original to something)
'new musical heading to west end' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'musical' becomes 'evita' (Andrew Lloyd Webber musical).
'heading to west end' says the letters should be written in reverse (letters written right to left or east to west).
'evita' backwards is 'ative'.
'n'+'ative'='NATIVE'
(Other definitions for native that I've seen before include "Original inhabitant" , "In a natural state" , "Endemic - aborigine" , "One locally born" , "Son" .)