Recommend healthy yodelling to help musical beginners when beat (6)
I believe the answer is:
rhythm
'beat' is the definition.
('rhythm' can be a synonym of 'beat')
'recommend healthy yodelling to help musical beginners' is the wordplay.
'beginners' suggests taking the first letters.
The initial letters of 'recommend healthy yodelling to help musical' is 'RHYTHM'.
'when' acts as a link.
(Other definitions for rhythm that I've seen before include "essence of some music?" , "Regular beat in music" , "(Poetic) metre" , "Cycle -- cadence" , "A musical essential" .)