Sentence:  Through 1911 and 1912 , as the Cubist facet-plane 's tendency to adhere to the literal surface became harder and harder to deny , the task of <WSD>keeping</WSD> the surface at arm's length fell all the more to eye-undeceiving contrivances . 
Meaning of the word marked with <WSD> tags:  keep in a certain state, position, or activity; e.g., "keep clean"