A little bit of everything? (6)
'a little bit of everything?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for atom that I've seen before include "Nucleus surrounded" , "Smallest component of an element" , "Small amount of matter" , "Part of molecule" , "Particle of matter now divided" .)
(Other definitions for sesame that I've seen before include "Opening word for the oilplant?" , "Open . . . . . . is a magic phrase to gain entry" , "Open .... is a pantomime cry" , "said to be effective in opening spell" , "Seed used in flavouring" .)