Musician having liver first (8)
I believe the answer is:
organist
'musician' is the definition.
(I know that organist is a type of musician)
'liver first' is the wordplay.
'liver' becomes 'organ' (I am not sure about this - if you are sure you should believe this answer much more).
'first' becomes 'ist' (ist resembles ost).
'organ'+'ist'='ORGANIST'
'having' is the link.
Can you help me to learn more?
(Other definitions for organist that I've seen before include "Accompanist, keyboard player" , "Church instr. player" , "Roasting (anag)" , "It groans for church musician" , "One plays in church usually" .)