Oddly loud, the instrument (4)
I believe the answer is:
lute
'instrument' is the definition.
(lute is a kind of instrument)
'oddly loud the' is the wordplay.
'oddly' means one should take alternating letters.
'loud'+'the'='loudthe'
The alternating letters of 'loudthe' are 'LUTE'.
(Other definitions for lute that I've seen before include "Subject to drugs" , "instrument that minstrel played" , "Ancient stringed instrument" , "Elizabethan stringed instrument" , "Old musical instrument" .)