Cher catches that is loud music associated with lament, as she's the one most familiar with The Dead (5,7)

'she's the one most familiar with the dead' is the definition.
I know nothing about this answer so I can't judge whether this works.

'cher catches that is loud music associated with lament as' is the wordplay.
'catches' means one lot of letters goes inside another.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'loud music' becomes 'f' (forte - musical term meaning loud).
'associated with' means one lot of letters go next to another.
'lament as' becomes 'mourn' (I've seen this before. I am not sure about the 'as' bit.).
'ie'+'f'+'mourn'='iefmourn'
'cher' enclosing 'iefmourn' is 'CHIEF MOURNER'.

Can you help me to learn more?