Carry across border readily available illustrations (4,3)
I believe the answer is:
clip art
'readily available illustrations' is the definition.
'carry across border' is the wordplay.
'carry' becomes 'cart' (carting is a kind of carrying**).
'across' indicates putting letters inside.
'border' becomes 'lip' (I've seen this in other clues).
'cart' placed around 'lip' is 'CLIP ART'.
(Other definitions for clip art that I've seen before include "Graphics files" , "computer images" , "Pre-drawn pictures usable in computer packages" , "Widely used images" .)