I study small picture on screen (4)
I believe the answer is:
icon
'picture on screen' is the definition.
'icon' can be an answer for 'picture' (icon is a kind of picture). I'm not certain of the 'on screen' bit.
'i study small' is the wordplay.
'study small' becomes 'con' (con can mean to study. I am not sure about the 'small' bit.).
'i'+'con'='ICON'
Can you help me to learn more?
(Other definitions for icon that I've seen before include "work of art" , "'Symbol, religious or computer (4)'" , "Representative symbol or religious painting" , "Religious (or computing) picture" , "Symbolic person or image" .)