Need examples of clue difficulties

[reborrell]

I'm teaching at a senior center about keeping minds active as we age.

I'm preparing a few sessions on crossword puzzles.  I have explained how the NYT puzzles get more difficult as the week progresses.

I'm looking for a sample of an answer, whose clue might change depending on the day of the week for the answer "nickel". 

Chemical element or low coin value
Atomic element 28
Valued between Lincoln & Roosevelt
Buffalo & Jefferson
discovered by Axel Cronstedt in 1751

Can anyone give me examples of showing how the same answer would warrant a different  question depending on the intended degree of puzzle difficulty or point me in the right direction for samples.

[mmcbs]

This web site (cruciverb) has an excellent database of clues and answers, which can be sorted by day of the week and by speficying only NYT entries you can enter your answer and see all the clues used for it by day of the week. Remember the degree of difficulty is not only a function of the clue, but also of the vocabulary (answers) and complexity/difficulty of the puzzle's theme.