Musical entertainment makes their pal go crazy (5,5)
I believe the answer is:
light opera
'musical entertainment' is the definition.
(I've seen this before)
'their pal go crazy' is the wordplay.
'crazy' indicates an anagram.
'their'+'pal'+'go'='theirpalgo'
'theirpalgo' is an anagram of 'LIGHT OPERA'.
'makes' acts as a link.
(Other definitions for light opera that I've seen before include "musical entertainment" , "'The Mikado', e.g." .)