You might try making a paragraph style and applying it to your text. It would include, among other settings:
Left alignment along with Adobe Single-Line Composer; not Adobe Paragraph Composer, which is often the default.
Why does Adobe Paragraph Composer leave gaps? Because it is trying to satisfy all the lines in the paragraph; not just one. Therefore it compromises some in order to satisfy other lines. A great way to help the Adobe Paragraph Composer is to also go to Justification settings. These include between-Word-spacing, within the Word Letter spacing, and individual letter glyph scaling. At default, only Word spacing is turned on. The other two are turned off.
So in a paragraph style, turn the other two on and allow the InDesign typesetting engine its full freedom of ability:
Word
80/100/120
Letter
-5/0/5%
Glyph Scaling
95/100/105%