Open extra time (5)
I believe the answer is:
overt
'open' is the definition.
(associated in meaning)
'extra time' is the wordplay.
'extra' becomes 'over' (both can mean left over).
'time' becomes 't' (abbreviation).
'over'+'t'='OVERT'
(Other definitions for overt that I've seen before include "Open and obvious" , "Plain and obvious" , "Open, not 1 across" , "____ is able to be seen" , "Openly displayed" .)