Organisation founded by William Booth (9,4)
I believe the answer is:
salvation army
'organisation founded by william booth' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for salvation army that I've seen before include "peaceful force" , "Christian group" , "The Booths' creation" , "The Booths' organisation" , "Christian body noted for social work and bands" .)