Revered object priest installed in church (5)
I believe the answer is:
relic
'revered object' is the definition.
(I've seen this before)
'priest installed in church' is the wordplay.
'priest' becomes 'eli' (biblical figure).
'installed in' is an insertion indicator.
'church' becomes 'rc' (abbreviation for Roman Catholic).
'eli' inserted inside 'rc' is 'RELIC'.
(Other definitions for relic that I've seen before include "Outdated survival" , "precious object" , "Fossil" , "church treasure" , "Left over item, sometimes sacred" .)