Images clicked on notebook's screen, first of all? (5)
I believe the answer is:
icons
'images' is the definition.
(I know this)
'clicked on notebook's screen first of all?' is the wordplay.
'clicked' becomes 'ic' (I can't justify this - if you can you should give a lot more credence to this answer).
'first of all?' suggests taking the first letters (I've seen 'first of all' mean this).
The first letters of 'on notebooks screen' is 'ons'.
'ic'+'ons'='ICONS'
(Other definitions for icons that I've seen before include "Screen symbols on 4 across" , "Religious paintings or computer symbols" , "Devotional paintings" , "Computer displays" , "Celebrities" .)