Sentence:  When he heard that Paul Whiteman was looking for singers to <WSD>replace</WSD> the Rhythm Boys , Mercer applied and got the job , `` not for my voice , I 'm sure , but because I could write songs and material generally '' . 
Meaning of the word marked with <WSD> tags:  substitute a person or thing for (another that is broken or inefficient or lost or no longer working or yielding what is expected)