Guess what the poet Donne was by profession (6)
I believe the answer is:
divine
'guess' is the definition.
(divine can mean to guess or work out)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for divine that I've seen before include "Find water" , "'To err is human, to forgive . . . . . .'" , "Guess" , "Appertaining to God" , "Like a god; delightful" .)