Heisenberg, I see you have an uncertainty about the clues with extra words. So did I. You can overthink it. Recall puzzles from the past where portions of answers need replacement of some letters by a symbol. Not easy because in all cases here the symbol needs to come either at the beginning of the word or in the second cell after an unchecked cell. I started with 6 Down. You should have ?SOME : just look at what the clue gives you. The others are similar.
I'm not quite with you, Unclued. Have you identified the 6 elements and done the colouring in/lines yet ? If so, as far as I'm concerned, you're finished. Never mind the instruction unless you're sending it in.
Unclued, to understand it fully, you have to think about the relevance of the symbols in the squares, and where they are positioned. Once you've carried out the instruction, what does the whole grid remind you of, in 2x2 form?
Hi supersub In the 3 Down clue B & B is the definition, with the word indicated cryptically by two elements reversed (including a Latin word) . Think along the lines of social _________ ! DULL is the one-word definition of a word (8 letters) meaning drab in a musical sense. Hybrid is one of the four EXTRA thematic words. The whole word is indicated by a compound anagram. As for me, I am stuck on the second part of that same clue (3 Down). Is the definition referring to "to deliver orally "? I have __ ENIS ! Any hints much appreciated. Am also very unsure about the highlighting. Do we end up with four black boxes ...or only three ? Otherwise I have located all six elements !