Mineworkers' lift, a hundred years old? (4)
'mineworkers' lift' is the definition.
(type of lift used in a mine)
'a hundred years old?' is the wordplay.
'a hundred' becomes 'c' (Roman numeral).
'years old?' becomes 'age' (I can't justify this - if you can you should believe this answer much more).
Can you help me to learn more?
(Other definitions for cage that I've seen before include "In places squirrel's nest", "Enclosure made from metal bars", "Imprison, confine", "One famous for creating silence", "Coop".)