Using distort (and possibly scaling) is probably the easiest way. Of course, this clip is probably SD and may not match your other HD clips. You might try doing the distort in Compressor and turn on Frame Controls and use the highest-quality setting for re-sizing. Compressor will do a better job of scaling than FCP. If the frame rates and/or codecs are different, then change that, too, in Compressor. For changing frame rates choose the highest-quality (in Frame Controls) for rate conversion.
John
MacPro 8-core 2.8GHz 8 GB RAM OS 10.5.8 QT7.6.4 Kona 3 Dual Cinema 23 ATI Radeon HD 3870, 24″ TV-Logic Monitor, ATTO ExpressSAS R380 RAID Adapter, PDE enclosure with 8-drive 6TB RAID 5
FCS 3 (FCP 7.0.2, Motion 4.0.2, Comp 3.5.2, DVDSP 4.2.2, Color 1.5.2)
Pro Tools HD w SYNC IO & 192 Digital I/O, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec Monitors, PrimaLT ISDN