A Roman emperor owned parts of Iran (7)
I believe the answer is:
hadrian
'a roman emperor' is the definition.
(I know that Hadrian is a roman emperor)
'owned parts of iran' is the wordplay.
'owned' becomes 'had' ('have' can be a synonym of 'own').
'parts of' indicates anagramming the letters.
'iran' anagrammed gives 'rian'.
'had'+'rian'='HADRIAN'
(Other definitions for hadrian that I've seen before include "Roman Emperor after Trajan" , "Imperial wall-builder" , "Wall-building Roman emperor" , "His wall crosses northern Britain" , "Roman emperor and wallbuilder" .)