Hi Andy the fiddler,
A compressor or normalize is probably not going to help here. Your best bet will be to apply a notch filter at the frequency of the hum.
Step 1: Establish the frequency of the hum
To do this choose a section of the recording where the background hum is obvious and there is not much other audio being recorded in the foreground. Place your cursor in this section and then select Tools->FFT. A spectral graph should be displayed. The hum should be represented as a peak in the graph. Mouse over the peak to find out what the frequency is.
Step 2: Remove the frequency
Select the range of audio from which you want to remove the hum. Click on the Levels tab and click the Equalize button. In the Eq dialog select the "Visual" tab. Select "Notch" from the Preset pull down list. In the options box which should be displayed select the start and end of the frequency range you would like to remove.
You may need to experiment with the numbers a little bit to get the best result possible and you it is possible that you will also notice undesirable effects occurring to the rest of your track. Unfortunately this can be hard to avoid if the frequency of the hum happens to be spectrally significant to the audio you are recording.
Hope this helps.
Regards,
Ben