Leaving when there's a summons to lunch, round about one (5)
I believe the answer is:
going
'leaving' is the definition.
(I know that leaving can be written as going)
'a summons to lunch round about one' is the wordplay.
I cannot quite understand how this works, but
'round' could be 'o' (round can mean a round object) and 'o' is found in the answer.
'about' could be 'in' (I've seen this in other clues) and 'in' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'when there's' is the link.
Can you help me to learn more?
(Other definitions for going that I've seen before include "Disappearing" , "Surface condition (that may get tough!)" , "Departure; current (rate)" , "fading" , "Running; leaving" .)