Ancient priest or book, outwardly of great age (4)
I believe the answer is:
ezra
'ancient priest' is the definition.
'ezra' can be an answer for 'priest' (I have seen 'Biblical priest ' mean 'ezra' so perhaps 'priest' could also mean 'ezra'). I am unsure of the 'ancient' bit.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for ezra that I've seen before include "Old Testament book - American poet Pound" , "-- Pound, US poet and critic 1885-1972" , "- Pound, twentieth century US poet" , "Fifteenth book of the Old Testament" , "High priest" .)