Crossword Genius

Cough or breathe on them! (3)

Ross

I believe the answer is:

hem

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

'cough' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.

'breathe on them' is the wordplay.
'HEM' is hidden in amongst the letters.
However, I am uncertain how this is indicated.

'or' acts as a link.

Can you help me to learn more?

(Other definitions for hem that I've seen before include "It draws attention to" , "Stitched edge of garment" , "Double-backed border of a garment" , "may attract attention" , "Finished edge of a piece of cloth" .)

I've seen this clue in the Evening Standard.
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