Marketing agents for car engine components (12)

'engine components' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Perhaps you can see a link between them that I don't see?

'marketing agents for car' is the wordplay.
I cannot quite see how this works, but
'for' could be 'to' (eg both can mean 'in the opinion of') and 'to' is found within the answer.
'car' could be 't' and 't' is located in the answer.
This explanation may well be incorrect...

Can you help me to learn more?