Smoother set of data (4)
I believe the answer is:
file
I believe this is a double definition.
'smoother' is the first definition.
(a file smooths something down)
'set of data' is the second definition.
(data file)
(Other definitions for file that I've seen before include "Cutting tool or line of people" , "Folder; rasp" , "Dossier; line of people" , "Folder; line" , "Tool for sawing through metal" .)