Surprisingly, age is no worry (7)
I believe the answer is:
Here is my best explanation:
'worry' is the definition.
'surprisingly age is no' is the subsidiary indication.
'surprisingly' is an anagram indicator.
'ageisno' anagrammed gives 'agonise'.
(Other definitions for agonise that I've seen before include "Be in torments of indecision", "Suffer extreme mental pain", "Struggle mentally", "Worry intensely", "Suffer great pain over something", "Torment oneself", "Fret, worry inordinately", "Worry greatly (over something); I go sane (anag.)", "Undergo great anguish" and "Suffer torment".)