Utter age, upset (4)
I believe the answer is:
emit
'utter' is the definition.
(I know that utter can be written as emit)
'age upset' is the wordplay.
'age' becomes 'time' (I've seen this before).
'upset' says the letters should be written in reverse.
'time' backwards is 'EMIT'.
(Other definitions for emit that I've seen before include "Small turtle" , "Issue" , "Broadcast" , "Give out or put forth" , "Give off or discharge" .)