What might be serious for patient wanting A&E? (3)

I believe the answer is:

cut

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

'ae?' is the definition.
Both the answer and definition are adjectives.
Maybe there's a link between them I don't understand?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for cut that I've seen before include "Slice, chop" , "Fail to attend" , "score" , "Sever, slice" , "Excise" .)

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