straight-arrow

Noun

straight arrow (plural straight arrows)

1. (US, informal) Someone who behaves according to conventional standards; one noted for honesty and integrity.
   • He was put down at first as a "straight arrow" — a do-gooder — and the description was sometimes accompanied by the cry, "ugh." as in old Westerns when the settler is shot by the wily redskin.1965 April 2, Paul O'Neil, “Bradley: good man and true”, in LIFE, volume 58, number 13, page 93
2. Used other than figuratively or idiomatically: see straight, arrow.
   • The goal can not be attained by a straight arrow flight.1908, Charles Francis Horne, The Technique of the Novel, page 28