Green’s Dictionary of Slang

a general positive intensifier, very, extremely; usu. in sporting contexts as clinking good and typcially of a racehorse or greyhound.

1862		Sporting Life 26 Mar. 3/2: [A] capital pack of harriers, with which one might always sure for a clinking good run.
1867		Sporting Life 23 Mar. 2/4: Wolsey, Sir Joseph Hawley [...] believed was a clinking good horse.
1868		Belfast News-Letter 17 Feb. 3/6: I have been informed [...] that Crumbs is a clinking good greyhound, and very likely to do credit to the kennel.
1869		Sporting Gaz. 26 June 14/3: [A] clinking good ball was sent at Mr Dale’s off stump.
1870		Sportsman (London) 5/: Monseigneur, Paganini, Don Carlos [...] all ‘clinking’ good horses, and great winners. In fact, a better field of horses [...] has not started for any race.
1889		Music Hall & Theatre Rev. 20 Apr. 155/2: Amphion [...] won in the style of a clinking good horse.
1890		Sporting Times 8 Feb. 3/3: Marseille, barring its odours, is a clinking good town—broad street, avenues of trees, and cafes everywhere.
1899		Boy’s Own Paper 15 Apr. 450: What a clinking little place, what pretty flowers, so homely too!
1903		A. Binstead Pitcher in Paradise 36: This mare’s been a-puttin’ in some clinkin’ fine work.
1908		Otago Witness 4 Mar. 90/2: Skirmisher was a clinking good colt.
1912		N.Z. Truth 15 June 3/3: A clinking good North v South match would be the means of convincing the unbelivers.
1912		E. Pugh Harry The Cockney 160: Clinking fine song!
1917		Van Loan ‘The Redemption Handicap’ in Old Man Curry 183: If this here Bismillah is such a hell-clinkin’ good race horse, how come they ain’t all bettin’ on him?