These are the first & last verses from a poem by Vernon Scannell. Unfortunately I have not been able to find anywhere on the web which will provide the bits which I did not copy out when I first came across it
First adjust your spectacles & take your pen,
(A pencil will serve equally well) & pick the easiest clue:
Here you are: five letters down – “What is Man?”
Clown, Rogue, Beast, or even Saint would do.
…
The snag about these clues is the alternatives are endless.
Write in the words faintly because you may have to alter them,
And be warned. When the puzzle is solved, & like a satisfied lover
You lean back sighing & sleepy, then you will find
That the black squares hide the secrets you will never uncover
