A number of pairs left out in a number of types of cars (6)

'cars' is the definition.
(coupe is a kind of car)

'a number of pairs left out in a number of types' is the wordplay.
I cannot quite see how this works, but
'number' could be 'e' (e is a kind of number) and 'e' is present in the answer.
'of' could be 'o' and 'o' is present in the answer.
'a number' could be 'c' (C is an example) and 'c' is found within the answer.
The remaining letters 'ups' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

'of' acts as a link.

Can you help me to learn more?