Middle Eastern port, a retreat (4)
I believe the answer is:
aden
'middle eastern port' is the definition.
(I've seen this in another clue)
'a retreat' is the wordplay.
'retreat' becomes 'den' (both can mean a lair or hideout).
'a'+'den'='ADEN'
(Other definitions for aden that I've seen before include "Dean out in the seaport city" , "Commercial capital of Yemen" , "foreign climes" , "Yemeni gulf" , "Yemeni port" .)