Don't join in the chorus (7)
I believe the answer is:
refrain
'chorus' is the definition.
(I know that chorus can be written as refrain)
'don't join in' is the wordplay.
I cannot really see how this works, but
'in' is present in the answer.
This explanation may well be incorrect...
'the' is the link.
Can you help me to learn more?
(Other definitions for refrain that I've seen before include "Break off" , "Do without" , "Desist, abstain" , "Main theme" , "Kindly desist - from song?" .)