Outside university, theologian is a failure (3)
I believe the answer is:
dud
'is a failure' is the definition.
(I've seen this before)
'outside university theologian' is the wordplay.
'outside' means one lot of letters goes inside another.
'university' becomes 'u'.
'theologian' becomes 'dd' (Doctor of Divinity degree).
'u' placed inside 'dd' is 'DUD'.
(Other definitions for dud that I've seen before include "Faulty" , "Bullet that fails to fire" , "Not functioning" , "Just a palindromic flop" , "A palindromic failure" .)