Unreliable version of criteria I rejected (7)
I believe the answer is:
erratic
'unreliable' is the definition.
(similar in meaning)
'version of criteria i rejected' is the wordplay.
'version of' is an anagram indicator.
'rejected' suggests deleting specific letters.
'criteria' with 'i' taken away is 'crteria'.
'crteria' anagrammed gives 'ERRATIC'.
(Other definitions for erratic that I've seen before include "Random, unreliable" , "Irregular in pattern or movement" , "Liable to sudden unpredictable change" , "Deep affection" , "Volatile" .)