Information a little upsetting (4)
I believe the answer is:
data
'information' is the definition.
(thesaurus)
'a little upsetting' is the wordplay.
'little' becomes 'tad'.
'upsetting' is a reversal indicator.
'a'+'tad'='atad'
'atad' backwards is 'DATA'.
(Other definitions for data that I've seen before include "Series of measurements" , "Organised information" , "Contents of some banks?" , "Numerical information" , "Raw facts" .)