Anomaly, irregularity (10)
I believe the answer is:
aberration
This clue is a double definition.
'anomaly' is the first definition.
(I've seen this before)
'irregularity' is the second definition.
(aberration is a kind of irregularity)
(Other definitions for aberration that I've seen before include "Unwelcome deviation from normal" , "moral lapse" , "Wandering" , "Mental lapse" , "irregularity" .)