<<<speaker started to break up or even distort the speaker's voice>>>
If all that happened was the volume went up and down or other graceful damage like that, then we'd be able to help you. Anything we do with clippers or compressors is just going to make the damage louder to fill up the holes in blue.
You could select just the damaged portion and apply Effect > Leveler on Heaviest, or maybe Effect > Compress Dynamics followed by Effect > Amplify to make the overall level come out to match. Compress Dynamics is Chris's Compressor which has to be installed as a separate tool.
In any exercise like this, you're far better off in Audacity 1.3.12 than Audacity 1.2.
http://audacityteam.org/download/
Audacity 1.2 is seriously old with very simple tools and a small toolbox.
Is there any way you can post some of the damage so we can listen?
Koz