I know it's a bit soon to be asking questions on this crossword but I am well into
it but would like clarification of the theme and instructions.
Can anyone help me with the preamble without letting out too much?
The three sets of three solutions are part of a well known quartet.
Once you have established the theme the fourth part will become clear. In the completed grid you will find the word in adjoining cells.
Once you have established the location in the grid you must highlight the letters in the colour which will be relevant and should be obvious.