Part of aircraft — standard practice ultimately over use (8)
I believe the answer is:
fuselage
'part of aircraft' is the definition.
(I've seen this before)
'standard practice ultimately over use' is the wordplay.
'standard' becomes 'flag' (I've seen this before).
'ultimately' indicates one should take the final letters.
'over' is an insertion indicator.
The last letter of 'practice' is 'e'.
'flag'+'e'='flage'
'flage' placed around 'use' is 'FUSELAGE'.
(Other definitions for fuselage that I've seen before include "Body of plane" , "Aircraft's body" , "part of plane" , "bodywork" , "Long body" .)