Sentence:  And listening to such a conversation one morning while taking a cup of chocolate in a cafe , Rousseau found himself bathed in perspiration , trembling lest his authorship become known , and at the same time dreaming of the startling effect he would make if he should <WSD>proclaim</WSD> himself suddenly as the composer . 
Meaning of the word marked with <WSD> tags:  declare formally; declare someone to be something; of titles