Inconstant criteria I must leave for revision (7)
I believe the answer is:
erratic
'inconstant' is the definition.
(I've seen this before)
'criteria i must leave for revision' is the wordplay.
'must leave' indicates named letters should be taken away.
'for revision' indicates an anagram (I've seen this in other clues).
'criteria' with 'i' removed is 'crteria'.
'crteria' with letters rearranged gives 'ERRATIC'.
(Other definitions for erratic that I've seen before include "Hit-or-miss" , "Liable to sudden unpredictable change" , "Cartier (anag.)" , "Sporadic" , "Rambling" .)