Green’s Dictionary of Slang

(US gay) a popular variety of post-gay liberation stereotype, often posing as a lumberjack type with checked flannel shirt, Levis, heavy boots etc.

1994–2003		(ref. to 1970s) KQED ‘The Castro’ homepage on KQED.org 🌐 The ‘Castro Clone’ look became a distinguishing feature of gay liberation in the 1970s, and signified a departure from previous stereotypes of gay dress and appearance.
1995–2003		S. Sheppard ‘Sex Talk’ at Gay.com 🌐 Then came the ‘Castro clone’ look, now a tired cliche, but then semi-revolutionary. Gone in the first flush of sexual liberation was the old butch-femme divide, replaced by flannel shirts and Levi’s 501s worn by tops and bottoms alike. It was an assertively butch look that said, ‘Real men do like to get plowed.’.
1998		R. Scott Rebecca’s Dict. of Queer Sl. 🌐 Castro clone — a gay man of the type who lives in or frequents The Castro. They all dress very similarly, tending towards very masculine attire and pumped-up, buffed good looks. The style is, in many ways, set by Tom of Finland.