Fly back without western guitar sound (5)
I believe the answer is:
twang
'guitar sound' is the definition.
(I've seen this in another clue)
'fly back without western' is the wordplay.
'fly' becomes 'gnat' (type of insect).
'back' says the letters should be written in reverse.
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'western' becomes 'w'.
'gnat' back-to-front is 'tang'.
'tang' placed around 'w' is 'TWANG'.
(Other definitions for twang that I've seen before include "Plucking sound - nasal tone" , "A nasal intonation in speech, or sound of guitar" , "brogue" , "Plucked string sound; nasal voice" , "Characteristically plucky" .)