Crossword Genius

Lids in part of combustion engine neither opening nor closing — really? (2,4,2)

Ross

I believe the answer is:

is that so

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

'really?' is the definition.
(I've seen this in another clue)

'lids in part of combustion engine neither opening nor closing' is the wordplay.
I cannot quite see how this works, but
'lids' could be 'hats' ('hat' can be a synonym of 'lid') and 'hats' is found in the answer.
'of' could be 'o' and 'o' is present in the answer.
The remaining letters 'ist' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Guardian.
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