yeah possibly a bad clutch, but you should be able to ease the clutch out in 1st with no gas and the car should start to roll. Now if you can in 3rd, then yes deffinitly a slipping clutch.
It could very well be a fuel / tuning issue also. You are more likely to notice clutch slippage issues in 3rd or high when there is more load being applied to the clutch.
Best test for a clutch slippage problem in most rear wheel drive 5speed cars is a hard throttle run in 4th gear from about 2500 to 4000 or 4500 RPM's. Being that 4th gear is a 1:1 ratio, the Tach and speedo neddles should increase at the same rate (i.e. they should follow eachother in sync). If the tach neddle increases faster then the speedo, then the clutch is slipping. The reason for doing it in the RPM range listed above is because most engine produce the most torque in that range and therefore slippage is most likely to accure in that area.