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' indicates an anagram (another version of the same letters).
'rejected' suggests deleting specific letters.
'criteria' with 'i' taken out 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" .)