Sentence:  Blake was a thorough gambler, and knew well how to make the most of the numerous chances which the turf afforded him. He had a large stud of horses, to the training and working of which he attended almost as closely as the person whom he paid for doing so. But it was in the betting-ring that he was most formidable. It was said, in Kildare Street, that no one at Tattersall's could beat him at a book. He had latterly been trying a wider <WSD>field</WSD> than the Curragh supplied him and had, on one or two occasions, run a horse in England with such success, as had placed him, at any rate, quite at the top of the Irish sporting tree. 
Meaning of the word marked with <WSD> tags:  (sports: area reserved for playing a game) An area reserved for playing a game or race with one's physical force.