The words clew, clue sound the same but have different meanings and spellings. Why do clew, clue sound the same even though they are completely different words?
The answer is simple: clew, clue are homophones of the English language.
A ball of yarn or thread.
Greek Mythology The ball of thread used by Theseus to find his way out of the labyrinth.
The cords by which a hammock is suspended.
Nautical One of the two lower corners of a square sail.
Something that serves to guide or direct in the solution of a problem or mystery.
To give (someone) guiding information: Clue me in on what's happening.
Variant of clew1.
Variant of clew1.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").