Singer or instrumentalist initially loves getting to grips with this music (8)
I believe the answer is:
oratorio
'this music' is the definition.
(oratorio is a kind of music)
'singer or instrumentalist initially loves getting to grips with' is the wordplay.
'singer' becomes 'rat' (I've seen this in another clue).
'initially' suggests taking the first letters.
'loves' becomes 'oo' (two O's - 'love' means zero in tennis).
'getting to grips with' indicates putting letters inside (one group of letters grips another).
The initial letter of 'instrumentalist' is 'i'.
'rat'+'or'+'i'='ratori'
'ratori' put inside 'oo' is 'ORATORIO'.
(Other definitions for oratorio that I've seen before include "Work such as Handel's Messiah" , "Outlying part of city" , "Handel's "Messiah", for instance" , "Noted work" , "E.g. Messiah or Elijah" .)