Green’s Dictionary of Slang

(gay) a brief love-affair, a fling.

1970		Queen’s Qly Fall 42/2: It’s better to have an ‘affairette’ with no strings attached than to pledge eternal and exclusive fidelity two seconds after the first climax [Simes:DLSS].
2003		Baker & Stanley Hello Sailor 57: [G]ay seafarers referred to these sorts of encounters as affairettes.