Unusual; peculiar (8)
I believe the answer is:
abnormal
I believe this clue is a double definition.
'unusual' is the first definition.
(similar in meaning)
'peculiar' is the second definition.
(I've seen this before)
(Other definitions for abnormal that I've seen before include "Deviating from the usual" , "Highly unusual" , "Freakish" , "Not typical or usual" , "Anomalous" .)