Cheer very quietly during a double somersault (7)
I believe the answer is:
applaud
'cheer' is the definition.
(thesaurus)
'very quietly during a double somersault' is the wordplay.
'very quietly' becomes 'pp'.
'during' indicates putting letters inside.
'double' becomes 'dual' ('dual' can be a synonym of 'double').
'somersault' is a reversal indicator.
'dual' written backwards gives 'laud'.
'a'+'laud'='alaud'
'pp' going inside 'alaud' is 'APPLAUD'.
(Other definitions for applaud that I've seen before include "Give an ovation" , "Cheer" , "Express approbation" , "Show acclaim" , "Commend audibly" .)