Oceanic rocklike substance formed from skeletons (5)

I believe the answer is:

coral

(Other definitions for coral that I've seen before include "Reef-forming skeletons" , "Reef-forming sea life" , "Material of many Pacific islands." , "Pink marine substance" , "Tiny animal forming reef" .)

I've seen this clue in The Telegraph.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.