Peer inside proper vehicle component (9)
I believe the answer is:
rearlight
'vehicle component' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'peer inside proper' is the wordplay.
'peer' becomes 'earl' (earl is a kind of peer).
'inside' means one lot of letters goes inside another.
'proper' becomes 'right' (associated in meaning).
'earl' going inside 'right' is 'REARLIGHT'.
Can you help me to learn more?
(Another definition for rearlight that I've seen is " part of vehicle".)