German city first in alphabet, with long name (6)
I believe the answer is:
aachen
'german city' is the definition.
(I've seen this before)
'first in alphabet with long name' is the wordplay.
'first in alphabet' becomes 'a' (1st letter of 'alphabet').
'with' says to put letters next to each other.
'long' becomes 'ache' (to long for something is to ache for it).
'name' becomes 'n' (common abbreviation e.g. on forms).
'a'+'ache'+'n'='AACHEN'
(Other definitions for aachen that I've seen before include "Aix-la-Chapelle's other name" , "old capital city" , "German city, Charlemagne's imperial capital" , "Whither good news was brought" , "German spa city" .)