DrSmellThis - Could you elaborate with an example?

It would be really helpful.
I also had some additional thoughts. Since we usually start with the base note, as it's the
longest lasting smell and the makes up for more than 50% of the smell, we can get away
with unwanted higher notes by hiding them with the middle notes (and similarly hiding the
unwanted middle notes with top notes). The question is what to do if the unwanted note
is tenacious and can't be really hidden by middle notes?
Also, I guess hiding with the middle notes simply means enhancing some other desired
effect?