Hi daorus,
Removing reverb is very difficult, but sometimes you can get decent results. In order to do this you will probably need to open the audio of your clip in WavePad which has more audio filtering options.
There are 2 basic strategies I would recommend you try:
1. Use a noise gate to attenuate low level noises which may help reduce the reverberations.
or
2. Use a VST plugin which is designed to remove reverb. If you google this you will see there are quite a few - some are free, some require licences. In order to use the VST in WavePad you will need to install the VST and then go to the effect tab in WavePad and click the "VST" button.
Hope this helps.
Regards,
Ben