To hear a couple of quintets will cheer you up! (7)
I believe the answer is:
hearten
'quintets will cheer you up' is the definition.
I can't judge whether this definition defines the answer.
'to hear a couple' is the wordplay.
'a couple' becomes 'ten' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'hear'+'ten'='HEARTEN'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for hearten that I've seen before include "Inspirit" , "Encourage in Teheran" , "Make (someone) more confident" , "given cheer" , "Inspire anew" .)