from www.tmz.com – TMZ has learned Rachel Uchitel has signed a deal to get naked for Playboy Magazine — but there’s a full-frontal catch.

Rachel hedged when we asked her about a Playboy offer on TMZ Live on Friday — but we found out that Tiger Woods’ #1 mistress has already struck an agreement. A source close to the mag tells us Rachel has the right to pull out any time before the shoot goes down — which is in three weeks.

We’re also told Rachel won’t be baring it all — just the backside … and the topside.

No word on when the spread will run in the mag.