Highly obvious to vocalise about pick of the bunch (9)
I believe the answer is:
screaming
'highly obvious' is the definition.
(screaming can mean very obvious)
'vocalise about pick of the bunch' is the wordplay.
'vocalise' becomes 'sing' (I've seen this before).
'about' means one lot of letters goes inside another.
'pick of the bunch' becomes 'cream' (cream can mean the best, as in cream of the crop).
'sing' going around 'cream' is 'SCREAMING'.
'to' is the link.
(Other definitions for screaming that I've seen before include "Yelling" , "Emitting sharp, piercing cries" , "Shrieking" , "Uttering sharp piercing cries" .)