Material in some eco-friendly clothing

HEMP

This fast-growing plant fiber is often used as a sustainable alternative to cotton.

This clue points to "hemp," a natural fiber used in sustainable fashion because it grows quickly without pesticides. The word "eco-friendly" hints at materials that are good for the environment, and hemp fits perfectly as a popular choice for green clothing. There’s no wordplay here—just a straightforward definition linking the clue to the answer.