Roughly, it means "easy (easily)", "light (lightly)", or "without effort".
"サクッ" is an onomatopoeia expressing light crushing sounds.
(for example: stepping on the snow, cutting fresh lettuce, eating cookies, etc.)
In English, したっぱ would mean "an underling". It is written as "下っ端" in kanji.
If a person is したっぱ of a team/organization, he/she is NOT a boss/chief/leader of that.