Trojan prince acquiring capital (5)
I believe the answer is:
paris
I believe this clue is a triple definition!
'trojan' is the first definition.
(mythical Trojan)
'prince' is the second definition.
(I have seen 'Old prince' mean 'paris' so perhaps 'prince' could also mean 'paris')
'acquiring' acts as a link.
'capital' is the third definition.
(Paris is the capital of France)
(Other definitions for paris that I've seen before include "Arc de Triomphe city" , "Helen's abductor" , "Prince of Troy - capital city" , "English chronicler" , "where plaster comes from?" .)