Part of sacred area (4)
I believe the answer is:
acre
'area' is the definition.
(I've seen this before)
'part of sacred' is the wordplay.
'part of' says the answer is hidden in the clue.
'ACRE' can be found hidden inside 'sacred'.
(Other definitions for acre that I've seen before include "Ancient city in Israel" , "Muslims here besieged" , "0.405 of a hectare" , "once occupied by Crusaders" , "Persistent tendency" .)