Increase for a clergyman (3)
I believe the answer is:
add
'increase' is the definition.
(I've seen this before)
'a clergyman' is the wordplay.
'clergyman' becomes 'dd' (Doctor of Divinity).
'a'+'dd'='ADD'
'for' acts as a link.
(Other definitions for add that I've seen before include "Reckon" , "Put together (numbers)" , "what a computer can do" , "Put together - attach" , "Sum up; say further" .)