Enclosure of wire or metal bars (4)
I believe the answer is:
cage
'enclosure of wire or metal bars' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cage that I've seen before include "American composer with centenary this year" , "Nicolas - - (films)" , "Wired enclosure" , "Put behind bars" , "Place of confinement" .)