While technically there is no "Clean Preset" on the Fender G-DEC 3, there are some Presets that have little or no gain, distortion or effects. A lot of users have found that using the Jazz Master amp setting with the Compressor off and the Timbre set to none will produce a non-effected, neutral sound. Also make sure that the treble, mid, and bass controls are all neutral.
NOTE: This can be accomplished in Fender FUSE by clicking "New" to create a new preset.