Dean lost port (4)
I believe the answer is:
aden
'port' is the definition.
(port in Yemen)
'dean lost' is the wordplay.
'lost' indicates anagramming the letters.
'dean' anagrammed gives 'ADEN'.
(Other definitions for aden that I've seen before include "Yemeni port" , "Dean is in the Yemen, strangely" , "Red Sea port" , "Yemeni gulf" , "Main port of Yemen" .)