Personal matter of dubious value is not raised online (6)
I believe the answer is:
tonsil
But I can't explain it at all! Could you help me understand?
(Other definitions for tonsil that I've seen before include "No slit at the base of the tongue" , "One of two at the back of the mouth" , "Mass of tissue" , "One often removed" , "Lymphatic tissue at the back of the mouth" .)