Sure is, but about 90% of my obscure knowledge of words comes from crosswords so after I while I just got used to them. I had to look up *why* "ut" was "do" for these two posts, but I've seen the usage before.
Also I agree with crosswhit's moan -- where did this clue appear, though?
Here's another example to illustrate this particular error:
Fish-meal starter -- brought into room (6)
(In this clue '--' represents an em dash)
The problem isn't that sub-note and fish-meal are incorrect in themselves but that hyphenated words shouldn't be split between definition and wordplay (Fish-meal's starter = F). It's fine to separate definition and wordplay with a dash however, so in this example replacing the hyphen by moving the dash (or with some other punctuation or link word) would solve the problem:
Fish -- meal's starter brought into room (meal's starter = m)