School of Buddhism (3)
I believe the answer is:
zen
'school of buddhism' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for zen that I've seen before include "Branch of Buddhism" , "Form of Buddhism that says enlightenment comes through meditation" , "Form of Buddhism stressing meditation" , "Form of Buddhism, emphasises meditation" , "branch of religion" .)