Public show accommodated by Essex police (4)
I believe the answer is:
expo
'public show' is the definition.
(I've seen this in another clue)
'accommodated by essex police' is the wordplay.
'accommodated by' says the answer is hidden in the clue.
'EXPO' is hidden in the letters of 'essex police'.
(Other definitions for expo that I've seen before include "Major international fair" , "World fair, e.g. Seville 1992" , "Large international exhibition" , "Show" , "Trade fair" .)