Please show your Appearance control field palette.
What you've done is add an additional Fill (gradient) on top of your type. You should do this, but choose the type characters and fill with none. The black underlying fline will dissappear from your text.
NOTE: the Appearance palette should be visable at all times, always! You're missing a lot of Illustrator's powerful styling features otherwise.
If I understand it in the right way, you may:
1) Click the live Type (which may be simple Type, Path Type, Area Type, or whatever) itself sp that you see the baseline(s) under it,
2) Set the Fill to None through the bottom of the Toolbox (this will make the Type invisible so that only the baseline(s) remain),
3) In the Appearance palette/panel flyout tick New Fill and click the Gradient in the bottom of the Toolbox,
4) Change the gradient as desired.
2) and 3) are steps already mentioned by PixelDoc.
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