Short meeting in Square (4)
I believe the answer is:
even
'square' is the definition.
(both mean 'owing nothing' as in 'we're all square')
'short meeting' is the wordplay.
'short' means to remove the last letter.
'meeting' becomes 'event' (meeting is a type of event).
'event' with its final letter removed is 'EVEN'.
'in' is the link.
(Other definitions for even that I've seen before include "like the numbers on two sides here" , "Equable" , "night" , "draw" , "time when sun goes down for the poet" .)