Record our getting older: it's depressing (12)
I believe the answer is:
discouraging
'depressing' is the definition.
(I've seen this before)
'record our getting older' is the wordplay.
'record' becomes 'disc' ('disc' can be a synonym of 'record').
'getting older' becomes 'aging' (I've seen this in other clues).
'disc'+'our'+'aging'='DISCOURAGING'
'it's' acts as a link.
(Other definitions for discouraging that I've seen before include "Depressing" , "Putting (someone) off" .)