Part of a space vehicle (6)
I believe the answer is:
module
'part of a space vehicle' is the definition.
('module' is part of 'space vehicle')
This is all the clue.
(Other definitions for module that I've seen before include "Short study course" , "Unit of a study course" , "Complete part (of spacecraft or course)" , "Detachable sub-unit" , "Standardised part in furniture - or spacecraft" .)