Good spirits (5)
'good spirits' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cheer that I've seen before include "Encourage - applaud" , "Lift the mood" , "Inspirit" , "Applaud; mood" , "Jolly" .)
(Other definitions for happiness that I've seen before include "State of well-being, contentment" , "Felicity" , "Contentment, joy" , "Cheer" , "Great contentment" .)