Instrument’s one needed earlier during part of flight (5)
I believe the answer is:
sitar
'instrument's' is the definition.
(sitar is a kind of instrument)
'part of flight' is the wordplay.
'part' becomes 'si' (si is a kind of part).
'of flight' becomes 'tar' (I am not sure about this - if you are sure you should believe this answer much more).
'si'+'tar'='SITAR'
'one needed earlier during' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
(Other definitions for sitar that I've seen before include "Hindu string instrument" , "Guitar-like instrument" , "Indian string instrument" , "It takes pluck" , "music-maker" .)