This is a riddle. Solve it if you can:-
My first letter is in light but never in day,
My second is found in both laughter and play,
My third is in scarlet and also in peach,
My fourth is in sand but not in a beach,
My last is in scarlet but never in green,
And my whole is quite solid yet often unseen.

Well, the riddle is certainly talking about the letters in the words given as clues.
The first letter could be any of the letters of the word: 'light'.
The second letter is either 'l' or 'a'.
The third letter is 'c', 'a' or 'e'.
the fourth letter is 's', 'n' or 'd'.
The last letter is 's', 'c', 'a', 'l' or 't'.
Try the different combinations to arrive at the word.