Not all authors are immortal (4)

I believe the answer is:

thor

'immortal' is the definition.
(Thor is an example)

'not all authors are' is the wordplay.
'not all' indicates the answer is hidden within the clue (only some of the letters).
'THOR' can be found hidden inside 'authors are'.

(Other definitions for thor that I've seen before include "The Thunderer" , "Mythical figure" , "Thunderous god" , "Norse hammer-wielding god" , "can be classed as immortal" .)

I've seen this clue in the Evening Standard.

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