It's Spander, duh.
It's one of those Xander sneaking off to dance at a gay(?) bar- for kicks, not as a job.
Spike finds out 'cause apparently it's a demon friendly bar and he's there to chill/get plastered/whatever.
Spike approaches Xander, but he's being all sneaky about it, using 'William's' accent and never letting Xander get a halfway decent look at him- this goes on for several encounters.
Random plot point: There's this thing about how everybody (human and demon) is trying to get into Xander's pants but he'll only go so far. I remember something about some guy actually managing to get Xander off and all the vamps being pissed and not believing it 'cause it was just a human.
There was also dark booth snogging.
Eventually, Spike comes clean, yadda, yadda, yadda...
I thought it was kitty_poker1's Dancing Fool, so I reread it last night... and close, but no cigar. So, yeah, umm, 'elp????
EDIT: Found it! FeatheredQuill's "Love of the loveless". *throws cookies and chocolaty confections at her saviours heuradys and alterian* Thanks guys!!!!!! *G*