Full-length garments for clergy (8)
I believe the answer is:
cassocks
'full-length garments for clergy' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cassocks that I've seen before include "Full-length garments for the clergy" , "Black vestments for a priest" , "Black frocks worn by priests" , "robes" , "Black vestments worn by priests" .)