It makes the lute less harmonious (4)
I believe the answer is:
rift
'it makes the lute less harmonious' is the definition.
The definition suggests a singular noun which matches the answer.
'it makes the' is the wordplay.
'it makes' becomes 'rif' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'rif'+'t'='RIFT'
Can you help me to learn more?
(Other definitions for rift that I've seen before include "Breach, rupture" , "Breach or quarrel" , "Breach - falling-out" , "Serious break in friendly relations" , "(Serious) break (in good relations)" .)