Potty lid or shape that's nearly round (10)

I believe the answer is:

spheroidal

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

'nearly round' is the definition.
'spheroidal' can be an answer for 'round' (I've seen this before). I am not certain of the 'nearly' bit.

'potty lid or shape' is the wordplay.
'potty' indicates anagramming the letters (potty can mean mad).
'lid'+'or'+'shape'='lidorshape'
'lidorshape' anagrammed gives 'SPHEROIDAL'.

'that's' is the link.

Can you help me to learn more?

(Other definitions for spheroidal that I've seen before include "ball" , "round" .)

I've seen this clue in The Times.

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