At short notice sent up information (4)
I believe the answer is:
data
'information' is the definition.
(data are bits of information)
'at short notice sent up' is the wordplay.
'short notice' becomes 'ad' (both can mean an advertisement. I am not sure about the 'short' bit.).
'sent up' shows that the letters should be reversed in order.
'at'+'ad'='atad'
'atad' written backwards gives 'DATA'.
Can you help me to learn more?
(Other definitions for data that I've seen before include "Contents of some banks?" , "Series of measurements" , "Facts and figures as fed to computers (4)" , "Known facts" , "information from bank" .)