Leave the centre of Exeter around eleven (4)
I believe the answer is:
exit
'leave' is the definition.
('exit' can be a synonym of 'leave')
'the centre of exeter around eleven' is the wordplay.
'the centre of' means to look at the middle letters.
'around' means one lot of letters goes inside another.
'eleven' becomes 'xi' (roman numeral).
The middle letters of 'exeter' are 'et'.
'et' enclosing 'xi' is 'EXIT'.
(Other definitions for exit that I've seen before include "walk away" , "Departure of actor" , "Leave the stage" , "Depart" , "Leave the building" .)