Cheering cup side missing final (3)
I believe the answer is:
tea
'cheering cup' is the definition.
(a cup of tea may cheer you up)
'side missing final' is the wordplay.
'side' becomes 'team' (a side is a sporting team).
'missing final' means to remove the last letter.
'team' with its last letter taken off is 'TEA'.
(Other definitions for tea that I've seen before include "Principally" , "TREE" , "Leaves for brewing" , "Plantation product" , "Afternoon meal (3)" .)