Surprised where kisser kissed? (10)
I believe the answer is:
gobsmacked
'surprised' is the definition.
'kisser kissed?' is the wordplay.
'kisser' becomes 'gob' (gobs or mouths can kiss).
'kissed?' becomes 'smacked' (a smacker is a loud kiss).
'gob'+'smacked'='GOBSMACKED'
'where' acts as a link.
(Other definitions for gobsmacked that I've seen before include "Stunned" , "Amazed" , "Flabbergasted" , "Dumbfounded" , "utterly astonished" .)