Bickering (4)
'bickering' is the definition.
(I know that bickering can be written as fuss)
This is the entire clue.
(Other definitions for fuss that I've seen before include "Worry without reason" , "Furore" , "Bother, ado" , "Needless excitement" , "Protest -- excitement" .)
(Other definitions for atit that I've seen before include "up to no good?" , "what birds (and bees) do?" , "in Congress" .)