Lightness (8)
'lightness' is the definition.
(I know that buoyancy is a type of lightness)
This is the entire clue.
(Other definitions for buoyancy that I've seen before include "capacity for flotation" , "Lightness" , "Tendency to keep float" , "showing resilience" , "Ability to float" .)
'lightness' is the definition.
(airiness is a kind of lightness)
This is all the clue.
(Other definitions for airiness that I've seen before include "Ethereality" , "Insubstantial quality" .)