Capital needed, get old man to invest cash, finally (7)
I believe the answer is:
baghdad
'capital' is the definition.
(capital of Iraq)
'get old man to invest cash finally' is the wordplay.
'get' becomes 'bag' (bag can mean to secure or obtain).
'old man' becomes 'dad' (synonyms).
'to invest' means one lot of letters goes inside another (back).
'finally' suggests the final letters.
The final letter of 'cash' is 'h'.
'bag'+'dad'='bagdad'
'bagdad' enclosing 'h' is 'BAGHDAD'.
'needed' is the link.
(Other definitions for baghdad that I've seen before include "Capital of Iraq" , "city abroad" , "capital abroad" , "Iraqi capital" .)