It is not an idiom, but a metaphor. I think the author intended us to understand that the guitarist was playing very energetically, very intensely, even wildly. It may also be a reference to the claw-hammer picking style of playing, but without more context we can't be sure.
This site is about using correct English, so please start each sentence with a capital letter.
As probus says, there are various possibilities. You'll find as you use this forum that good answers always need context. A fragment of a sentence, without even a verb, doesn't give potential responders much to go on!
Very fast guitar playing especially in metal music is refered to as "shredding". To "Claw apart" would also be to shred. Related musical descriptors from jazz- let it rip, ripped it, blew it up, tore it apart.
It depends on the context, though. It might be more literal: In a drunken rage, he slugged his boss, smashed up his car, set his house on fire, and clawed apart his favorite guitar with his bare hands.
I've been playing guitar since 1968, and I've never heard playing, including shredding and claw-hammering, referred to as clawing apart a guitar. That doesn't mean that the suggestions above are wrong. It just means there might be other possibilities.
Without knowing more about what was said, we can't tell.