Excluded over infiltrating organisation (3,2,2)
I believe the answer is:
out of it
'excluded' is the definition.
(I've seen this before)
'over infiltrating organisation' is the wordplay.
'over' becomes 'o' (cricket abbreviation).
'infiltrating' is an insertion indicator.
'organisation' becomes 'outfit' (outfit is a kind of organization).
'o' put inside 'outfit' is 'OUT OF IT'.
(Other definitions for out of it that I've seen before include "Excluded from participation" , "Forlorn" , "unaware of what's going on" , "is not included" , "Drunk < , unaware what is happening" .)