After Jack, Sid turns up in the Doctor's vehicle (6)
I believe the answer is:
tardis
'the doctor's vehicle' is the definition.
I know nothing about this answer so I can't judge whether this works.
'after jack sid turns up' is the wordplay.
'after' is a charade indicator (letters next to each other).
'jack' becomes 'tar' (I've seen this before).
'turns up' says the letters should be written in reverse.
'sid' back-to-front is 'dis'.
'tar' put next to 'dis' is 'TARDIS'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for tardis that I've seen before include "Doctor Who's time machine" , "Dr Who's time machine" , "Doctor Who's transport" , "Doctor Who's ship" , "Famous time machine" .)