The term 'Giant Slayer' refers to a person who has killed or defeated a giant. In this crossword, the solutions are David (5 letters), JACK (4 letters), and APOLLO (6 letters). David is a figure from the Bible who famously slew Goliath with a slingshot. JACK is a character from English folklore who killed a giant with a magical beanstalk. APOLLO is a Greek god who killed the giant Python with his bow and arrows.