Armenia's capital (7)
(Other definitions for tbilisi that I've seen before include "Capital city of Georgia" , "Georgian city" , "Georgian place" , "Georgian capital" .)
'armenia's capital' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for yerevan that I've seen before include "Capital of Armenia" , "ancient capital" , "east European city" .)