Foe of alarmed Yemen (5)

I believe the answer is:

enemy

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

'foe' is the definition.
(I know that foe can be written as enemy)

'alarmed yemen' is the wordplay.
'yemen' can be anagrammed to 'ENEMY'.
But, I am unsure how the anagram is indicated.

'of' is the link.

Can you help me to learn more?

(Other definitions for enemy that I've seen before include "Yemen (anag.)" , "Hostile opponent" , "Armed adversary" , "Time" , "Foe, adversary" .)

I've seen this clue in The Mirror.

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