A blow. I’ll give you a clout on your jolly nob; I’ll give you a blow on your head. It also means a handkerchief. Cant. Any pocket handkerchief except a silk one.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
To Chuck * Clouted ShoonNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes