Green’s Dictionary of Slang

a chimney sweep.

[1772		Leeds intelligencer 11 Feb. 3/3: An honest Chimney-sweeper tricked a farmer out of twenty pounds [...] The too credulous country-man, supposing him to be a clergyman by his garb, took everything he said, for gospel].
1834		Flash Minstrel! in Spedding & Watt (eds) Bawdy Songbooks (2011) I 108: [song title] Up the Flew, or, the Knowing Clergyman [...] Clergy he got burnt so bad, / To give the trade up he was glad.
1848		Flash Dict. in Sinks of London Laid Open.
1890–1904		Farmer & Henley Sl. and Its Analogues.