Fuss about a section of flight (5)
I believe the answer is:
stair
'section of flight' is the definition.
(I've seen this before)
'fuss about a' is the wordplay.
'fuss' becomes 'stir' ('stir' can be a synonym of 'fuss').
'about' is an insertion indicator.
'stir' enclosing 'a' is 'STAIR'.
(Other definitions for stair that I've seen before include "Tarsi (anag)" , "One step in a series" , "Tread and riser" , "Support on which to step" , "means to go down" .)