Dance beat good? Not half! (5)
I believe the answer is:
tango
'dance' is the definition.
(Tango is a dance)
'beat good? not half' is the wordplay.
'beat' becomes 'tan' (tan can mean to beat or hit).
'not half' indicates taking half.
'good' halved is 'go'.
'tan'+'go'='TANGO'
(Other definitions for tango that I've seen before include "Colourful dance from Argentina" , "Dance music" , "Rhythmic movement" , "reputedly takes two" , "Steps" .)