Actor, inept, has to be sacked (8)

I believe the answer is:

thespian

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'actor' is the definition.
(I know that actor can be written as thespian)

I don't understand the rest of the clue.

(Other definitions for thespian that I've seen before include "A formal actor" , "Stage actor" , "Actor; relating to drama" , "cast member" , "He paints (anag)" .)

I've seen this clue in The Times and The Sun.

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