Halfway through the day (4)
I believe the answer is:
noon
'halfway through the day' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for noon that I've seen before include "when only mad dogs go out?" , "12 o'clock" , "See 8" , "Twelve o'clock in the day" , "The middle of the day" .)