single word requests - What is the term for a person who doesn't waste time?

Without context, it's difficult to understand what you mean by "waste time". It's too broad and may refer to: leisure time and entertainment, commuting, stopping to work and chat for a few minutes, watch soap operas and sitcoms, wait for someone, wait in line, etc.

If it's about work, a workaholic is a person who compulsively works for long hours and finds no time for leisure.

• workaholic" - (noun) a person who chooses to work a lot : a person who is always working, thinking about work. - My brother is a real workaholic who almost never takes time off. MW