Sent back a little information (4)
I believe the answer is:
data
'information' is the definition.
(data are bits of information)
'sent back a little' is the wordplay.
'sent back' says the letters should be written in reverse.
'little' becomes 'tad' (both can mean a small amount).
'a'+'tad'='atad'
'atad' back-to-front is 'DATA'.
(Other definitions for data that I've seen before include "Collected information" , "Raw facts" , "Facts and figures as processed by computer" , "Numerical facts" , "Facts and figures as fed to computers (4)" .)