Clergyman sliced with iron during golf, so blasted (9)
I believe the answer is:
deafening
'golf so blasted' is the definition.
I can't judge whether this defines the answer.
'clergyman sliced with iron during' is the wordplay.
'clergyman' becomes 'dean' (dean is a kind of clergyman).
'sliced with' becomes 'ing' (I can't justify this - if you can you should believe this answer much more).
'iron' becomes 'Fe' (chemical symbol for iron).
'during' indicates putting letters inside.
'dean'+'ing'='deaning'
'deaning' going around 'fe' is 'DEAFENING'.
Can you help me to learn more?
(Other definitions for deafening that I've seen before include "Very loud" , "Noisy" .)