Hi Guys,
When you add an effect in MixPad, you are adding the effect to the entire track. The clips themselves are not actually changed, rather they are fed through the track's effect chain when you playback or mix down. This allows you to keep making adjustments to your effect parameters without having to constantly reapply the changes and thereby degrade your original recordings.
If you want to raise the volume of just one clip then I would suggest using the volume envelope. Again, this will keep your original recording in tact, but still get the amplification you are looking for.
If you still need to apply a permanent amplification (or any other effect), then you can right click the track and select "Edit Clip...". This will open the clip in WavePad and you will have access to a vast array of filters and effects you can use to alter the clip. When you save your result, you are saving the changes to that clip permanently, so if you may need to go back to the old clip then it is better to make a copy first!
Hope this helps you guys get where you need to go!
Regards,
Ben