The Don puffed on his cigar and said, "Santino, what do you think?" Hagen knew what Santino would say. Sonny was chafing at being under the Don's thumb.
What is the mean of chafing here? I've found several meaning of that word in a dicitionary
Is meaning 3.
Become or make annoyed or impatient because of a restriction or inconvenience
suitable here?
Become or make annoyed or impatient because of a restriction or inconvenience
Is the right definition here.
If you look at the next few lines it makes more sense.
The Don puffed on his cigar and said, "Santino, what do you think?" Hagen knew what Santino would say. Sonny was chafing at being under the Don's thumb. He wanted a big operation of his own. Something like this would be perfect.
Sonny didn't like being controlled by the Don. He wanted to have some control of his own - which he would get if this operation was set up.
Your given definition is a good choice. Sonny is annoyed/impatient because Don has power over him.
It is a metaphor in this example. Chafing is rubbing which causes heat or irritation and in this case the unstated comparison is with a dog or similar creature struggling against (for example) leather restraints in a desire for freedom. Sonny is looking for some way to escape Don's control.
Edit: in fact, it's really a mixed metaphor as Sonny is said to be under Don's thumb. However, both phrases are really clichés: metaphors that have lost their power by constant repetition.
