Very young cat I lost in ancient city (7)
I believe the answer is:
babylon
'ancient city' is the definition.
'Babylon' can be an answer for 'city' (Babylon is an example). I am unsure of the 'ancient' bit.
'very young cat i lost in' is the wordplay.
'very young' becomes 'baby'.
'cat i' becomes 'on' (I am not sure about this - if you are sure you should believe this answer much more).
'lost' becomes 'l' (abbreviation in sporting league tables).
'in' indicates putting letters inside.
'baby'+'on'='babyon'
'babyon' placed around 'l' is 'BABYLON'.
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" , "Ancient city on Euphrates noted for luxury and wickedness" , "Ancient city on Euphrates once noted for sin and wickedness" , "Ancient Mesopotamian city" , "Ancient ruined city in modern Iraq" .)