What clergy wear suit mostly needing belt? (7)
I believe the answer is:
cassock
'what clergy wear' is the definition.
I can't judge whether this definition defines the answer.
'suit mostly needing belt?' is the wordplay.
'suit' becomes 'case' ('case' can be a synonym of 'suit').
'mostly' means to remove the last letter.
'needing belt?' becomes 'sock' (I can't explain this - if you can you should believe this answer much more).
'case' with its final letter taken off is 'cas'.
'cas'+'sock'='CASSOCK'
Can you help me to learn more?
(Other definitions for cassock that I've seen before include "Is it a habit of the clergy" , "Long clerical garment" , "Clerical garb" , "Ankle-length garment worn by priests and choristers" , "Clergyman's gown" .)