Abnormal, insincere (9)
I believe the answer is:
unnatural
I believe this is a double definition.
'abnormal' is the first definition.
(I know that abnormal can be written as unnatural)
'insincere' is the second definition.
(thesaurus)
(Other definitions for unnatural that I've seen before include "Strange" , "Annual rut may be abnormal" , "Freakish" , "Abnormal; not spontaneous" , "Lacking normal feelings of, say, affection" .)