Cold and old behind bars (5)
I believe the answer is:
caged
'behind bars' is the definition.
(I've seen this before)
'cold and old' is the wordplay.
'cold' becomes 'C' (eg on taps).
'and' says to put letters next to each other.
'old' becomes 'aged' (similar in meaning).
'c'+'aged'='CAGED'
(Other definitions for caged that I've seen before include "In a zoo?" , "in prison" , "Confined behind bars" , "Shut up" , "Cooped up" .)