American friend attending a trial in capital city (8)
I believe the answer is:
budapest
'capital city' is the definition.
(I've seen this before)
'american friend attending a trial' is the wordplay.
'american friend' becomes 'bud' (US term for friend).
'attending' says to put letters next to each other.
'trial' becomes 'pest' (both can mean an annoying person).
'bud'+'a'+'pest'='BUDAPEST'
'in' acts as a link.
(Other definitions for budapest that I've seen before include "capital location" , "Put beads in the European city" , "Capital city on the Danube" , "Capital of Hungary" , "capital of Europe" .)