Catch sight of friend sent back for computers (7)
I believe the answer is:
laptops
'for computers' is the definition.
(laptop is a kind of computer)
'catch sight of friend sent back' is the wordplay.
'catch sight of' becomes 'spot' (to spot is to notice or catch sight of).
'friend' becomes 'pal' (pal can mean a friend).
'sent back' says the letters should be written backwards.
'spot'+'pal'='spotpal'
'spotpal' written backwards gives 'LAPTOPS'.
(Other definitions for laptops that I've seen before include "PCs" , "more than one PC" , "Portable computers" .)