Quite crafty, absorbing atmosphere (6)
I believe the answer is:
fairly
'quite' is the definition.
(I've seen this before)
'crafty absorbing atmosphere' is the wordplay.
'crafty' becomes 'fly' (fly can mean shrewd or crafty).
'absorbing' indicates putting letters inside.
'atmosphere' becomes 'air' (synonyms).
'fly' enclosing 'air' is 'FAIRLY'.
(Other definitions for fairly that I've seen before include "Equitably; passably" , "Quite" , "To a moderate degree" , "In an evenhanded manner - somewhat" , "Moderately" .)