Boy's story probed by a theologian (6)
I believe the answer is:
laddie
'boy's' is the definition.
(laddie can mean a young boy)
'story probed by a theologian' is the wordplay.
'story' becomes 'lie' (story can mean a fabrication).
'probed by' indicates putting letters inside (I've seen this in other clues).
'theologian' becomes 'DD' (Doctor of Divinity degree).
'a'+'dd'='add'
'lie' enclosing 'add' is 'LADDIE'.
(Other definitions for laddie that I've seen before include "(Scots) boy" , "Youngster" , "Sonny" , "Scottish boy" , "Child" .)