Hades lovely when shorn of rocks formed deep underground (8)

I believe the answer is:

plutonic

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'deep underground' is the definition.
Both the answer and definition are adjectives. Maybe they are linked in a way I don't understand?

'hades lovely when shorn of rocks' is the wordplay.
'hades' becomes 'Pluto' (synonyms).
'lovely when shorn of rocks' becomes 'nic' (I can't justify this - if you can you should give a lot more credence to this answer).
'pluto'+'nic'='PLUTONIC'

'formed' is the link.

Can you help me to learn more?

(Another definition for plutonic that I've seen is " Solidified molten rock".)

I've seen this clue in The Independent.

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