Belief in infinite netherworld (5)

I believe the answer is:

tenet

'belief' is the definition.
(synonyms)

'in infinite netherworld' is the wordplay.
'in' indicates the answer is hidden within the clue.
'TENET' is hidden in the letters of 'infinite netherworld'.

(Other definitions for tenet that I've seen before include "Teaching" , "Rule" , "Dogma or principle" , "Doctrine held to be true" , "Fundamental belief" .)

I've seen this clue in The Guardian.

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