Refrain from putting burden mainly on American (6)
I believe the answer is:
chorus
'refrain' is the definition.
(I know that refrain can be written as chorus)
'burden mainly on american' is the wordplay.
'burden' becomes 'chore' (I've seen this before).
'mainly' means to remove the last letter.
'on american' becomes 'us' (abbreviation for United States. I am not sure about the 'on' bit.).
'chore' with its final letter taken away is 'chor'.
'chor'+'us'='CHORUS'
'from putting' is the link.
Can you help me to learn more?
(Other definitions for chorus that I've seen before include "Vocal composition" , "Group singing together" , "Organized group of singers" , "See 19" , "Band of singers and dancers" .)