Crossword Genius

What you're right about the earl having on his car?

Ross

I think it could be either:

Which length description are you looking for?:

4,5

9*

rear light

I'm a little stuck... Click here to teach me more about this clue!

'what you're right about the earl having on his car?' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.

'right about the earl having on his car?' is the wordplay.
'right' becomes 'rt' (abbreviation as in Rt Hon- the Right Honourable).
'about' indicates putting letters inside.
'having' is a charade indicator (letters next to each other).
'on his car?' becomes 'igh' (I can't explain this - if you can you should give a lot more credence to this answer).
'earl'+'igh'='earligh'
'rt' enclosing 'earligh' is 'REAR-LIGHT'.

Can you help me to learn more?

(Other definitions for rear light that I've seen before include "late display of driving" , "car component" , "safety device!" , "shiner" , "part of car" .)

I've seen this clue in the Evening Standard.
Want a hint initially instead of a full solution? Install my app