Certain meditator (4)
I believe the answer is:
yogi
'certain meditator' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for yogi that I've seen before include "Adherent of a Hindu philosophy" , "philosophy student" , "Master of a Hindu philosophical system" , "teacher of well-being" , "Follower of a Hindu philosophy involving mind and body" .)