Make less dense (E, not I) (6)
I believe the answer is:
rarefy
(Other definitions for rarefy that I've seen before include "Make thinner" , "Make more refined" , "Make less solid; a ferry (anag.)" , "Fry are (anag.)" , "Refine" .)
I believe the answer is:
rarefy
(Other definitions for rarefy that I've seen before include "Make thinner" , "Make more refined" , "Make less solid; a ferry (anag.)" , "Fry are (anag.)" , "Refine" .)