Main body of an aircraft (8)
I believe the answer is:
fuselage
'main body of an aircraft' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for fuselage that I've seen before include "Aircraft's body" , "part of aircraft" , "is often up in the air" , "Central body of an aeroplane" , "part of plane" .)