Senior lawyer on at the end of Prime Time (3)
I believe the answer is:
Here is my best explanation:
'time' is the definition.
(I've seen this before)
'senior lawyer on at the end of prime' is the subsidiary indication.
'senior lawyer' becomes 'ag' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on' says to put letters next to each other.
'at the end of' says to take the final letters.
The final letter of 'prime' is 'e'.
(Other definitions for age that I've seen before include "Historical period", "Maturity", "Get older", "Time in years", "Years lived so far", "Grow older", "Get old", "16/18 [INDUSTRIAL REVOLUTION]", "Long period" and "period of history".)