OT high priest (3)
I believe the answer is:
eli
'ot high priest' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for eli that I've seen before include "Priest at Shiloh (Samuel)" , "- Wallach, US actor" , "Shiloh priest (Bible)" , "Samuel's teacher (OT)" , "Biblical high priest" .)