Cawley's father, also called Tom, played for the two Sheffield clubs in the Nineteenth Century, including the 1890 FA Cup final which Wednesday lost 6-1 to Blackburn Rovers. In 1886, Cawley made a stand when disgruntled Wednesday players who wanted to turn professional broke away to form Sheffield Rovers. When the new club met to formally adopt professionalism, Cawley pleaded that Wednesday should be given one last chance, which the board agreed to and the initiative was abandoned.

Tom junior signed for Sheffield Wednesday around 1909, but moved on to Leeds City in 1914. He had to wait almost three years for his first team debut for the Peacocks.

During preparations for the 1915/16 season, it seemed likely that Cawley would make the step up into City's first-team, but in the end he was overlooked in favour of Arthur Price. According to Old Ebor in the Yorkshire Evening Post on 27 November: 'Cawley, another City reserve, is playing with Sheffield Wednesday - and with distinction, too - with the consent of the Leeds management. They could not find a place for him in their first-team and so willingly agreed to his playing for the Wednesday, for whom his father has done many years' service.'

Cawley played, with the City directors' permission, and did well for Wednesday against Leeds in December, when, according to the Evening Post, 'On the Sheffield side, Cawley, the Leeds City reserve player of last season, who has been permitted to assist the Owls this season, confirmed the favourable reports which have been received as to his recent form. The experience he is gaining with the First League team should be very useful when the time comes for him to rejoin Leeds City.'

Cawley continued to turn out with Wednesday in 1916/17, again playing against his host club, on 14 October when City won 1-0. He finally made his first team bow for Leeds as replacement for Levi Thorpe at left-half when the Peacocks lost 2-0 at Bradford Park Avenue in a Subsidiary Tournament game on 7 April 1917, retaining his place for the 1-0 victory at Huddersfield two days later.

He played on the opening day of the 1917/18 season, against The Wednesday, but reverted to playing for the Sheffield side again following this when Arthur Price was free to play for Leeds.

He eventually broke through as a City regular, in the problem position on the right wing, eight weeks later and was a regular on the flank for the rest of the campaign, scoring six times in 26 appearances. This run included both games of the two-legged play off for the unofficial league championship against Stoke in May 1918. When his shot struck the bar in the first game at Elland Road, Billy Hibbert followed up to open the scoring.

Cawley continued to feature at the start of the following season before giving way to Tom Hall shortly after the Armistice. He ended his City days with ten goals from 43 appearances.

In August 1919, Cawley signed up for Rotherham County and proved his versatility over the next three seasons. He was content to play in a number of positions when others were unavailable, though he only managed 36 games before moving to Worksop Town and then Scunthorpe & Lindsey United.

He died in 1980.