Shout in approval (5)
I believe the answer is:
cheer
'shout in approval' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cheer that I've seen before include "Applaud with shouts" , "hurrah" , "Applaud vocally, hurray etc" , "Shout hooray" , "Vocal sound of applause" .)