Its said to stun for a long time (4)
I believe the answer is:
days
'time' is the definition.
(day is a unit of time)
'its said to stun for a long' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
The remaining letters 'dys' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for days that I've seen before include "` `They are not long, the .... of wine and roses' ' (Dowson)" , "See 1 down" , "Units of time" , "Sevenths of a week" , "Periods (of week)" .)