Combine with two sailors in an investment producing capital (5,5)
I believe the answer is:
addis ababa
'capital' is the definition.
(capital of Ethiopia)
'combine with two sailors in an investment' is the wordplay.
'two sailors' can mean two replacements for 'sailor'.
'combine with' becomes 'add'.
'sailor' becomes 'ab' (abbreviation for able seaman).
'sailor' becomes 'ab' (abbreviation for able seaman).
'in' means one lot of letters goes inside another.
'an investment' becomes 'isa' (Individual Savings Account).
'ab'+'ab'='abab'
'abab' put within 'isa' is 'isababa'.
'add'+'isababa'='ADDIS ABABA'
'producing' acts as a link.
(Other definitions for addis ababa that I've seen before include "Capital of Ethiopia" , "Ethiopian capital" , "Unaccompanied" , "place in Africa" , "African city" .)