To play by ear is better entertaining (9)
I believe the answer is:
improvise
'to play by ear' is the definition.
(thesaurus)
'is better entertaining' is the wordplay.
'better' becomes 'improve' ('improve' can be a synonym of 'better'**).
'entertaining' indicates putting letters inside.
'is' placed within 'improve' is 'IMPROVISE'.
(Other definitions for improvise that I've seen before include "Extemporise" , "Talk without notes" , "Spontaneously create" , "Create without preparation" , "wing it" .)