Pint-sized idol finally performing in old city (7)
I believe the answer is:
babylon
'old city' is the definition.
(I've seen this before)
'pint-sized idol finally performing' is the wordplay.
'pint-sized' becomes 'baby' (I can't justify this - if you can you should give a lot more credence to this answer).
'finally' suggests the final letters.
'performing' becomes 'on' (as in being on stage).
The final letter of 'idol' is 'l'.
'baby'+'l'+'on'='BABYLON'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for babylon that I've seen before include "Bony lab in the old city of Mesopotamia" , "Chief city of ancient Mesopotamia" , "Ancient city in Mesopotamia notorious for excess" , "Place of sorrowful exile (or of luxury and decadence)" , "Ancient Mesopotamian city" .)