Start for starter WSJ Crossword Clue

Think about what initiates action without external prompting.

????: A person's essential being that distinguishes them from others, especially considered as the object of introspection or reflexive action.

The clue suggests the beginning or origin of something related to 'starter.' '????-starter' is a common term for someone who begins tasks independently, and '????' is the starting part of this term.

___-driving car, "There are three things extremely hard: steel, a diamond, and to know one's ___.": Poor Richard's Almanack, "To thine own ___ be true", Narcissist’s priority, The "s" in the acronym "scuba"