A cattle market is the sort of place that male first year undergraduate students at university go all the time in an effort to get their end away, but this invariably results in the guilty boys leaving the venue with an itch.
The term derives because the women in these clubs are essentially showing themselves off in the hope of being taken home, just as cattle are shown off at cattle markets in the hope of being sold.
Pete: "We can't go there, it's a right cattle market!"
"Ooh, I was in Creation last night and pulled this slapper - now I have an itch! Serves me right for visiting such a cattle market!"
"Let's go down to Gatecrasher - I hear it's a real cattle market down there!"