The phrase "a certain lightness" is correct and usable in written English.
It can be used to describe a quality or feeling that is not heavy or burdensome, often in a metaphorical sense.
Example: "The novel has a certain lightness that makes it enjoyable to read, even during serious moments."
Alternatives: "a particular ease" or "an element of buoyancy".
"There's a certain lightness about it".
He had a certain lightness of being.
"There's a certain lightness that's wonderful, and it's so ready for culture.
"They were added to give the house a certain lightness," Knox says.
When you're not burdened with that, there's a certain lightness to your life – my buttons aren't being pushed".
A certain lightness and transparency offset the stone, as a generous, large-paned apartment building, with workspace at the bottom, lies behind the masonry.
Wrapped up against the cold and in sunglasses, she wields the phone with a certain practised lightness that suggests an affectless, unengaged and deeply ephemeral exercise – as if she's taking her portrait literally without thought, let alone any feelings one way or the other about the human crisis in the background.
At a certain point, a lightness of being takes over.
The overall effect is a certain coolness and lightness — edging into crisp detachment — at the expense of some of Disney Hall's remarkable warmth.
Adapting Austen's wit was another challenge, as he could not use it "because it's almost all in the author's voice telling us about characters, with a certain wit or lightness that came from the characters themselves.
If they had done so, it would have confirmed what the Europeans hoped was a certain kinship: the Asian's lightness contrasted with the darkness of the purportedly noncivilized within "Asia" as a whole in a way that closely paralleled how Europe contrasted with the darkness of its own non-Christian others, notably Africans.
