Green’s Dictionary of Slang

1. a prostitute.

1953		K. Tennant Joyful Condemned 47: What does she do? Slugs a guy like a cro on a beat.
1966		Trimble 5000 Adult Sex Words and Phrases.

2. a woman.

1953

K. Tennant Joyful Condemned 322: Fair-haired cro with her hair cut short across the front.