さっさと is an onomatopoeic word meaning quickly, but not for mobile or moving things. For example, a common saying is さっさとしろよ。meaning "Hurry up and do it!" but saying * トムさんはさっさと走った。"Tom ran quickly." would be incorrect. If you search for さっさ you will see the result at the very top. The と in this case is a quotation marker. If you need an alternate way of saying this, you can try 早速 or すぐ. If you need another onomatopoeic word, ちゃんと or きりきり might be the closest match.
さっと is also extremely colloquial. Avoid it unless you are with friends.
Also, さっとしろよ。just doesn't sound right to me.
So, technically not one word but two... yet in every single example sentence it appears as さっさと.
I wonder if there's a case for having that form in the dictionary? Or at least having the sentence parser recognise it as さっさ + と.
Alternative form (さっさと)?
Google Translate says さっさと means "quickly". In this case I'm prepared to believe what it tells me, but that form's not listed here. (It is on Wiktionary, for what it's worth.)