Ye old form of singing (5)
I believe the answer is:
yodel
'singing' is the definition.
(I have seen 'Falsetto singing ' mean 'yodel' so perhaps 'singing' could also mean 'yodel')
'ye old form' is the wordplay.
'form' is an anagram indicator.
'ye'+'old'='yeold'
'yeold' anagrammed gives 'YODEL'.
'of' is the link.
(Other definitions for yodel that I've seen before include "Sing by alternating between normal voice and falsetto" , "Sing warblingly" , "unusual singing" , "Sing (Swiss style)" , "Sing in high trilling tone like Swiss mountaineer" .)