Even less like an oil painting in Louvre with its frame retouched (10)

I believe the answer is:

unlovelier

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

'oil painting in louvre with its frame retouched' is the definition.
I know nothing about this answer so I can't judge whether this works.

'even less like an' is the wordplay.
I cannot quite see how this works, but
'like' could be 'love' (loving is a kind of liking) and 'love' is found within the answer.
'an' could be 'i' (Roman numeral for one) and 'i' is found within the answer.
This may be the basis of clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Guardian.

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