A priest that is round about fifty? (3)
I believe the answer is:
eli
'a priest' is the definition.
(biblical figure)
'that is round about fifty?' is the wordplay.
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'round' shows that the letters should be reversed in order.
'about' means one lot of letters goes inside another.
'fifty?' becomes 'L' (Roman numeral).
'ie' reversed gives 'ei'.
'ei' enclosing 'l' is 'ELI'.
(Other definitions for eli that I've seen before include "Man's name" , "Old Testament priest, the prophet Samuel's teacher" , "Highest priest at Shiloh" , "Biblical teacher of Samuel" , "Samuel's teacher (OT)" .)