One in mad cult troubles about certain religious writings (8)

I believe the answer is:

talmudic

'about certain religious writings' is the definition.
(relating to the Talmud)

'one in mad cult troubles' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'troubles' indicates anagramming the letters (I've seen 'trouble' mean this).
'mad'+'cult'='madcult'
'madcult' is an anagram of 'talmudc'.
'i' placed within 'talmudc' is 'TALMUDIC'.

(Another definition for talmudic that I've seen is " related to fundamental code".)

I've seen this clue in The Times.

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