Sentence:  He improvised as he went along , completing a life-size clay figure , then bought yards of an inexpensive material from a draper , wet the lightweight cloth in a basin and covered it over with <WSD>clay</WSD> that Argiento brought from the bank of the Tiber , to the consistency of thick mud . 
Meaning of the word marked with <WSD> tags:  a very fine-grained soil that is plastic when moist but hard when fired