Best people in chant making a lot of noise (9)
I believe the answer is:
screaming
'making a lot of noise' is the definition.
'best people in chant' is the wordplay.
'best people' becomes 'cream' (I've seen this before).
'in' indicates putting letters inside.
'chant' becomes 'sing' (I've seen this before).
'cream' placed within 'sing' is 'SCREAMING'.
(Other definitions for screaming that I've seen before include "Emitting sharp, piercing cries" , "Shrieking" , "Yelling" , "Uttering sharp piercing cries" .)