LA Times Crossword
September 15, 2015
Jerome Gunderson

One word in the list below holds the key to explaining all of the other words. . It has to do with something you can't do. Wordplay is fair play.

CASTLE
BALLET
BERET
DEBUT
FILLET
HEART
LISTEN
MORTGAGE
WRESTLE

Answer:

The key word is HEART. 

Explanation:

If you read HEART as two words, you get HEAR T. You can't HEAR T in any of the other list words.