Try This For Size

Try this for size:

Figure out or forfeit the prize

And here’s the clue:

Not a red herring, but a passe-partout

In leisurely pursuit, Holmes excels

Hercule exercises those little grey cells

Crosswords have you to thank

Without them, unfulfilled and blank

Tally Ho! I’m ahead of the chase

Bring me to ground or sink without trace

Hey diddle diddle, at the end of the riddle

I’m staring you in the face.