The burden is "Don't!" (7)
I believe the answer is:
refrain
'the burden' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for refrain that I've seen before include "Main theme" , "Stop activity" , "Desist, abstain" , "Do without" , "Abstain; chorus" .)