Sing melody badly apart from introduction (5)
I believe the answer is:
yodel
'sing' is the definition.
(I know this)
I cannot understand how the rest of the clue works.
(Other definitions for yodel that I've seen before include "Sing like some Alpine dwellers" , "Sing in Tyrolean fashion" , "mountain air?" , "Practise Alpine singing" , "Sing partially falsetto" .)