Crew heading off after year in stinking capital city (9)
I believe the answer is:
pyongyang
'capital city' is the definition.
(capital of North Korea)
'crew heading off after year in stinking' is the wordplay.
'crew heading off' becomes 'ang' (I can't explain this - if you can you should believe this answer much more).
'after' is a charade indicator (letters next to each other).
'year' becomes 'y'.
'in' is an insertion indicator.
'stinking' becomes 'pongy' (pong can mean a bad smell).
'y' inserted within 'pongy' is 'pyongy'.
'ang' put after 'pyongy' is 'PYONGYANG'.
(Other definitions for pyongyang that I've seen before include "Capital of North Korea" , "North Korean capital" .)