Cheerleaders' activity (7)
I believe the answer is:
yelling
'cheerleaders' activity' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for yelling that I've seen before include "Bellowing" , "Shouting loudly" , "Screaming" , "Hollering, howling" , "Uttering loud cries" .)