Deportment of unusual air and grace (8)
I believe the answer is:
carriage
'deportment' is the definition.
(I've seen this before)
'unusual air and grace' is the wordplay.
'unusual' is an anagram indicator.
'and' says to put letters next to each other.
'air'+'grace'='airgrace'
'airgrace' anagrammed gives 'CARRIAGE'.
'of' acts as a link.
(Other definitions for carriage that I've seen before include "Bodily posture or wheeled vehicle" , "Transportation" , "Conveyance, its cost" , "Posture; conveyance" , "Railway passenger coach" .)