Leave around eleven, Eastern Time (4)
I believe the answer is:
exit
'leave' is the definition.
(I know that leave can be written as exit)
'around eleven eastern time' is the wordplay.
'around' indicates putting letters inside.
'eleven' becomes 'xi' (Roman numerals).
'eastern' becomes 'e'.
'time' becomes 't' (abbreviation).
'e'+'t'='et'
'xi' placed within 'et' is 'EXIT'.
(Other definitions for exit that I've seen before include "farewell!" , "Way out sign" , "Departure of actor" , "Way to go!" , "Actor's departure" .)