Being not wary? Strange (7)
I believe the answer is:
uncanny
'strange' is the definition.
(thesaurus)
'being not wary?' is the wordplay.
'being not' becomes 'un' (I've seen this in other clues).
'wary?' becomes 'canny' (both can mean careful**).
'un'+'canny'='UNCANNY'
(Other definitions for uncanny that I've seen before include "Weird, unnatural" , "Weird; supernatural" , "Strange, beyond the normal" , "Weird, unearthly" , "Odd, strange" .)