Hell, belonging to a firm is immaterial (12)

I believe the answer is:

discorporate

'immaterial' is the definition.
('discorporate' can be similar in meaning to 'immaterial')

'hell belonging to a firm' is the wordplay.
'hell' becomes 'dis' (I've seen this in other clues).
'belonging to a firm' becomes 'corporate'.
'dis'+'corporate'='DISCORPORATE'

'is' is the link.

I've seen this clue in The Guardian.

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