Reversible doctrine? (5)

I believe the answer is:

tenet

This clue is a double definition.

'reversible' is the first definition.

'doctrine' is the second definition.
(both can mean a belief or value)

(Other definitions for tenet that I've seen before include "Item of belief" , "Belief - maxim" , "A belief or creed - a palindrome" , "Doctrine; principle held" , "A palindromic doctrine or creed" .)

I've seen this clue in The Guardian, The Telegraph and the Evening Standard.

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