Good in German city the morning after (8)
I believe the answer is:
hangover
'morning after' is the definition.
(I've seen this before)
'good in german city' is the wordplay.
'good' becomes 'g' (abbreviation).
'in' means one lot of letters goes inside another.
'german city' becomes 'hanover' (city in Germany).
'g' going within 'hanover' is 'HANGOVER'.
'the' acts as a link.
(Other definitions for hangover that I've seen before include "problem arising?" , "Morning after state following from 17 Across" , "morning-after feeling?" , "Unpleasant aftermath of drinking binge" , "Headache from drink" .)