Sentence:  He dropped his earlier and delightful hamming , which <WSD>is</WSD> about the only way to handle the old war horse called `` Charley's Aunt '' , and let himself go with as an appealing an `` Amy '' as anybody could ask . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)