One in vehicle going to old African city (5)
I believe the answer is:
cairo
'african city' is the definition.
(I've seen this before)
'one in vehicle going to old' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'vehicle' becomes 'car' (car is a kind of vehicle).
'going to' means one lot of letters go next to another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'i' inserted inside 'car' is 'cair'.
'cair'+'o'='CAIRO'
(Other definitions for cairo that I've seen before include "Port upstream from the Nile delta" , "Egyptian capital" , "City near the Nile delta" , "Capital city on the Nile" , "Capital of Egypt" .)