Possibly Smiley’s one deception (4)
I believe the answer is:
icon
'possibly smiley's' is the definition.
(a smiley face is an example)
'one deception' is the wordplay.
'one' becomes 'i' (roman numeral).
'deception' becomes 'con' (I've seen this before).
'i'+'con'='ICON'
(Other definitions for icon that I've seen before include "Adored person" , "Symbol activated by mouse" , "Representation on wooden panel of saint" , "Venerated picture" , "Image - sex symbol" .)