Activity around a component of flight (5)
I believe the answer is:
stair
'component of flight' is the definition.
(I've seen this before)
'activity around a' is the wordplay.
'activity' becomes 'stir' (stir can mean activity or fuss).
'around' is an insertion indicator.
'stir' enclosing 'a' is 'STAIR'.
(Other definitions for stair that I've seen before include "Rising step" , "A step on the way up or down" , "Step as part of flight" , "Bit of a flight!" , "one on the way up" .)