Sentence:  “And they would certainly take offence, were their son to be accused of theft.” “It would stir them up like an egg whisk. I mean, however well they know that Wilbert is a <WSD>pincher</WSD>, they don't want to have it rubbed in.” [...]<!--ch. XII--> “And if ever a man needed to be constantly under an eye, it's the above kleptomaniac.” “The what?” “Haven't you been told? Wilbert's a <WSD>pincher</WSD>. [...] He pinches things. Everything that isn't nailed down is grist to his mill.” 
Meaning of the word marked with <WSD> tags:  A person or thing that pinches, as in stealing; e.g. a thief or kleptomaniac.