Leading setter's charges immediately reduced (9)
I believe the answer is:
prominent
'leading' is the definition.
(I've seen this in another clue)
'setter's charges immediately reduced' is the wordplay.
'setter's' becomes 'mine' (what belongs to the crossword setter).
'charges' indicates putting letters inside (charge can mean to charge into something).
'immediately' becomes 'pronto' (pronto can mean at once or quickly).
'reduced' means to remove the last letter.
'pronto' with its final letter taken away is 'pront'.
'mine' going into 'pront' is 'PROMINENT'.
(Other definitions for prominent that I've seen before include "Projecting; famous" , "Important; protuberant" , "sticking up" , "Conspicuous or outstanding" , "Important, famous" .)