Balkan citizen turning up on time in French port (5)
I believe the answer is:
brest
'french port' is the definition.
(port city in Brittany)
'balkan citizen turning up on time' is the wordplay.
'balkan citizen' becomes 'serb' (I've seen this in another clue).
'turning up' says the letters should be written in reverse.
'on' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'serb' written backwards gives 'bres'.
'bres'+'t'='BREST'
'in' acts as a link.
(Other definitions for brest that I've seen before include "Naval base in Brittany" , "French warships here in Brittany" , "French Atlantic naval base" , "Breton port" , "French port" .)