Fixed TV that’s no longer working? (4-3)

I believe the answer is:

dead-set

I'm a little stuck... Click here to teach me more about this clue!

'fixed' is the definition.
(I've seen this in another clue)

'tv that's no longer working?' is the wordplay.
I cannot really see how this works, but
'tv' could be 'set' (television set) and 'set' is found within the answer.
'no longer working?' could be 'dead' (I've seen this in another clue) and 'dead' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Times.

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