Law enforcement agencies were scouring Clark County last night for a federal pris oner who escaped from a Charleston Ave. psychiatrist’s office yesterday afternoon. Leroy C. Manning, 41, of 5912 Idle St. was in the office of Dr. William D. O’Gorman, 1924 Charleston Blvd., under going psychiatric examina tion. Left alone for a few minutes, Manning saw his chance and fled through a side window. Reported stolen at approx imately the same time was a 1963 white Ford pick-up be longing to Southwest Gas Corp. which is believed, by (Continued on Page %)