Focus Louis, for one, found in meditative practice (4,2)
I believe the answer is:
zero in
'focus' is the definition.
(I've seen this before)
'louis for one found in meditative practice' is the wordplay.
'louis for one' becomes 'roi' (I've seen this in another clue).
'found in' indicates putting letters inside.
'meditative practice' becomes 'zen' (I've seen this in another clue).
'roi' put within 'zen' is 'ZERO IN'.
(Other definitions for zero in that I've seen before include "head for the target" , "Direct on to a point" , "Aim" , "focus" .)