Direct is Latin with the -ct- cluster intact, from directus, the past participle of dirigere, "to set straight, to guide." That is dis-, "apart," plus regere, "to guide, keep straight," from a root meaning "to move in a straight line" — the same root behind regular, rule, right and royal. English liked the cluster enough to keep it in act, fact, instinct and a hundred others; French tended to wear such things down, which is why the same root reaches English through French as dress and address.
The word came in during the late 1300s, and its first English sense is the narrow one of addressing a letter or words to someone. Pointing or aiming at something followed by about 1400, governing or regulating behaviour by the early 1400s, and ordering or ordaining by the 1650s. Directing a play or film is from 1913.
direct (v.) late 14c., directen , "to write or address (a letter, words)" to someone, also "to point or make known a course to," from Latin directus past participle of dirigere "set straight, arrange; give a particular direction to, send in a straight line; guide" a thing, either to something or according to something, from dis- "apart" (see dis- ) + regere "to direct, to guide, keep straight" (from PIE root *reg- "move in a straight line"). Compare dress ; address . Sense of "to point or aim in a straight line toward a place or an object" is from c. 1400. Meaning "to govern, regulate as to behavior, prescribe the course or actions of" is from early 15c. Sense of "to order, ordain" is from 1650s. Sense of "to write the destination on the outside of a letter" had emerged by 17c. In reference to plays, films, etc., "to supervise and control the making of," it is attested from 1913. Related: Directed ; directing . also from late 14c. direct (adj.) c. 1400, "straight, undeviating, not crooked," from Old French direct (13c.) and directly from Latin directus "straight," adjectival use of past participle of dirigere "to set straight," from dis- "apart" (see dis- ) + regere "to direct, to guide, keep straight" (from PIE root *reg- "move in a straight line"). Meaning "plain, expressive, not ambiguous" is from 1580s. also from c. 1400
direct came in through Latin, and its spelling follows that family's conventions.
How that family writes these sounds
| /kt/ | -ct-, a cluster Latin tolerated and English inherited wholeact, fact, direct, instinct |
What gives it away on the page
| -ct- | A cluster Latin tolerated and English inherited wholesale.act, fact, direct, instinct |