Agitates about a flight! (6)
I believe the answer is:
stairs
'flight' is the definition.
(I've seen this before)
'agitates about a' is the wordplay.
'agitates' becomes 'stirs' (stirring is a kind of agitating).
'about' is an insertion indicator.
'stirs' placed around 'a' is 'STAIRS'.
(Other definitions for stairs that I've seen before include "4 and 8 (to the cockney)" , "Series of steps" , "Flights of steps" , "Interior means of ascent" , "A flight of indoor steps" .)