Particular case not in position (6)
I believe the answer is:
stance
'position' is the definition.
(stance is a kind of position)
'particular case not in' is the wordplay.
'particular case' becomes 'instance' (I've seen this before).
'not' is a deletion indicator.
'instance' with 'in' taken out is 'STANCE'.
(Other definitions for stance that I've seen before include "Attitude (of body, mind)" , "Way of standing, like golfer addressing ball" , "Position assumed by upright person" , "position when batting" , "Pose, for a golfer say" .)