Green’s Dictionary of Slang

understandings n.2

[pun + play on SE understanding, a relationship + stand n. (2), an erection]

1. an act of sexual intercourse.

[UK]‘The Female Pawnbroker’ in Convivialist in Spedding & Watt (eds) Bawdy Songbooks (2011) IV 24: The female Pawnbroker I mean, / I’d give you a right under-standing).

2. of a woman, sexual conquests.

[UK]Farmer & Henley Sl. and Its Analogues.