Challenged measure adopted by theologian (5)
I believe the answer is:
dared
'challenged' is the definition.
(daring is a kind of challenging)
'measure adopted by theologian' is the wordplay.
'measure' becomes 'are' (are is a kind of measure**).
'adopted by' is an insertion indicator (I've seen this in other clues).
'theologian' becomes 'dd' (Doctor of Divinity degree).
'are' placed into 'dd' is 'DARED'.
(Other definitions for dared that I've seen before include "was bold enough" , "Risked" , "Was brave enough" , "Ventured" , "Had the courage (to do something)" .)