Crucifix set on a beam or screen at the entrance to the chancel of a church (4)
I believe the answer is:
rood
(Other definitions for rood that I've seen before include "Old land measure and large cross in a church" , "Area equal to 40 square rods" , "Crucifix in church; one quarter of an acre" , "Crucifix; old land area measure" , "Crucifix in entrance, set back" .)