Piece on Sixties youth that's taken over country (7)
I believe the answer is:
kingdom
'taken over country' is the definition.
'kingdom' can be an answer for 'country' (kingdom is a kind of country). I'm unsure of the 'taken over' bit.
'piece on sixties youth' is the wordplay.
'piece' becomes 'king' (king is a kind of piece).
'on sixties youth' becomes 'dom' (I can't justify this - if you can you should give a lot more credence to this answer).
'king'+'dom'='KINGDOM'
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for kingdom that I've seen before include "Regal realm" , "All the animals" , "Country with royal head of state" , "Domain of a monarch" , "For one animal" .)