An image for one to study (4)
I believe the answer is:
icon
'an image' is the definition.
(I know that image can be written as icon)
'one to study' is the wordplay.
'one' becomes 'i' (Roman numeral).
'to study' becomes 'con' (con can informally mean to study).
'i'+'con'='ICON'
'for' acts as a link.
(Other definitions for icon that I've seen before include "Famous and admired person" , "work of art" , "Very important person" , "Image on computer screen representing facility" , "famous personality" .)