In heart of eastern country, a capital city (6)
I believe the answer is:
tirana
'capital city' is the definition.
(I've seen this before)
'in heart of eastern country a' is the wordplay.
I cannot really understand how this works, but
'country' could be 'iran' (I've seen this before) and 'iran' is found in the answer.
'a' is present in the answer.
A single letter 't' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tirana that I've seen before include "Albanian capital" , "Take a train to the capital of Albania" , "capital city" , "Take a train to Albania's capital (6)" , "foreign capital" .)