Middle of the day (4)
I believe the answer is:
noon
'middle of the day' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for noon that I've seen before include "Twelve during daylight" , "Twelve o'clock, midday" , "Twelve o'clock in the day" , "when only mad dogs go out?" , "12 o'clock" .)