Through barrier, behold king in city (8)
I believe the answer is:
florence
'city' is the definition.
(Florence is an example)
'through barrier behold king' is the wordplay.
'through' is an insertion indicator (some letters go through others).
'barrier' becomes 'fence' (fence is a kind of barrier).
'behold' becomes 'lo' ('lo' is an archaic exclamation meaning 'look!').
'king' becomes 'R' (abbreviation for rex, king in Latin).
'lo'+'r'='lor'
'fence' going around 'lor' is 'FLORENCE'.
'in' acts as a link.
(Other definitions for florence that I've seen before include "Ms Nightingale in great Italian city" , "Brunelleschi's birthplace" , "Name of girl ? city" , "Capital of Tuscany" , "place in Italy" .)