Breeze from the south crossing German capital (4)
I believe the answer is:
riga
'capital' is the definition.
(Riga is an example)
'breeze from the south crossing german' is the wordplay.
'breeze' becomes 'air' (synonyms).
'from the south' says the letters should be written in reverse (in a down clue, letters go up).
'crossing' indicates putting letters inside.
'german' becomes 'g' (abbreviation).
'air' back-to-front is 'ria'.
'ria' going around 'g' is 'RIGA'.
(Other definitions for riga that I've seen before include "capital in Europe" , "Baltic capital city" , "Fix a rig up here for the Latvians" , "A rig in Latvia" , "Latvian capital" .)