A theologian to be put as an extra (3)
I believe the answer is:
add
'be put as an extra' is the definition.
I can't tell whether this definition defines the answer.
'a theologian' is the wordplay.
'theologian' becomes 'DD' (Doctor of Divinity degree).
'a'+'dd'='ADD'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for add that I've seen before include "what a computer can do" , "Combine (numbers)" , "Reckon" , "Tot; append" , "problem for hyperactive children" .)