Spinning mechanism supplies oxygen to interior of posh car (5)
I believe the answer is:
rotor
'posh car' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'spinning mechanism supplies oxygen to interior' is the wordplay.
'spinning mechanism supplies' becomes 'rr' (I can't justify this - if you can you should believe this answer much more).
'oxygen' becomes 'O' (O is the chemical symbol for oxygen).
'interior' indicates putting letters inside.
'o'+'to'='oto'
'rr' enclosing 'oto' is 'ROTOR'.
'of' is the link.
Can you help me to learn more?
(Other definitions for rotor that I've seen before include "Machine part that turns around" , "Spinner" , "Chopper blade" , "Arm moving" , "Mechanical turning part" .)