Without slack is a phrase that describes a situation in which there is no room for error or leniency. The term can be used to describe a situation in which someone is working hard and efficiently, or when someone is being held to a high standard. The crossword solutions for this term are tautly (6 letters), TENSE (5 letters), and TAUT (4 letters). Tautly means tightly or firmly, and is often used to describe a rope or string that is pulled tight. TENSE is an adjective that describes a feeling of anxiety or stress. Finally, TAUT is an adjective that describes something that is stretched tight or pulled together.