A retreat East of Suez (4)

I believe the answer is:

aden

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

'east of suez' is the definition.
The definition suggests a singular noun which matches the answer.

'a retreat' is the wordplay.
'retreat' becomes 'den' (both can mean a lair or hideout).
'a'+'den'='ADEN'

Can you help me to learn more?

(Other definitions for aden that I've seen before include "Yemeni gulf" , "somewhere on the Arabian peninsula" , "Dean is out in the Middle Eastern port" , "Dane in seaport of Yemen" , "Port city of Yemen" .)

I've seen this clue in The Globe and Mail.

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