Cheer international going round lake (4)
I believe the answer is:
clap
'cheer' is the definition.
(I've seen this before)
'international going round lake' is the wordplay.
'international' becomes 'cap' (sportsperson who competes internationally).
'going round' is an insertion indicator (some letters go around others).
'lake' becomes 'L' (geographical abbreviation).
'cap' going around 'l' is 'CLAP'.
(Other definitions for clap that I've seen before include "Applaud in manual way" , "Make sound of applause" , "A meeting of hands" , "Pat" , "Applaud manually" .)