Sentence:  By one <WSD>o'clock</WSD> the place was choc-a-bloc. […] The restaurant was packed, and the promenade between the two main courts and the subsidiary courts was thronged with healthy-looking youngish people, drawn to the Mecca of tennis from all parts of the country. 
Meaning of the word marked with <WSD> tags:  In conjunction with a numeral, indicates the time within a twelve-hour period (midnight to noon or noon to midnight), specifically the time when the hour hand of a clock points precisely to the symbol or marking corresponding to the designated numeral.