Sentence:  The first thing every morning when she washed her face she could see the scar on her chin where he 'd cut her with a boot cleat , and maybe she saw him heaving it again , the dirty <WSD>sock</WSD> popping out as it flew . 
Meaning of the word marked with <WSD> tags:  hosiery consisting of a cloth covering for the foot; worn inside the shoe; reaches to between the ankle and the knee