X-ray lamp so involved regarding fits (10)

I believe the answer is:

paroxysmal

'regarding fits' is the definition.
(I know this)

'x-ray lamp so involved' is the wordplay.
'x ray' becomes 'x-ray' (synonyms).
'involved' is an anagram indicator (involved can mean confusing or complex).
'xray'+'lamp'+'so'='xraylampso'
'xraylampso' is an anagram of 'PAROXYSMAL'.

I've seen this clue in The Independent.

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