Clean up the fourth Mediterranean city (3,4)
I believe the answer is:
tel aviv
'mediterranean city' is the definition.
(Israeli city)
'clean up the fourth' is the wordplay.
'clean' becomes 'valet' (valet can mean to clean).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'the fourth' becomes 'iv' (Roman numerals for four).
'valet' backwards is 'telav'.
'telav'+'iv'='TEL AVIV'
(Other definitions for tel aviv that I've seen before include "Capital of Israel" , "city on the Mediterranean coast" , "Israel's administrative capital" , "Evil Vat imposed on Israeli city" , "Second largest city of Israel" .)