Colon, in many an emoticon (4)
I believe the answer is:
eyes
'colon in many an emoticon' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for eyes that I've seen before include "Looks at - organs" , "Blemishes on potatoes" , "Spots on a peacock's tail" , "''Drink to me only with thine ...'' (Johnson)" , "Storm centres" .)