Leaders of nation obtain overwhelming news at midday (4)
I believe the answer is:
'midday' is the definition.
'leaders of nation obtain overwhelming news' is the wordplay.
'leaders of' says to take the initial letters.
The initial letters of 'nation obtain overwhelming news' is 'NOON'.
'at' acts as a link.
(Other definitions for noon that I've seen before include "High time of day?", "[LUNCHTIME] ?", "The middle of the day", "Twelve o'clock, midday", "See 8".)