Emphasise result of demand exceeding capability? (6)

I believe the answer is:

stress

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'emphasise' is the definition.
(I know that emphasise is a more specific form of emphasise)

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for stress that I've seen before include "Tension; emphasis" , "Emphasize" , "Lay emphasis on - it's a strain" , "Tension - accent" , "Emotional tension" .)

I've seen this clue in The Times.

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