Definition: "slippery stuff"

This is an anagram - look for an indicator word that suggests mixing or rearranging letters

'Loose' is the anagram indicator - rearrange the letters found in 'gravel's' to get your 7-letter answer

Answer: VERGLAS | 'Loose' indicates an anagram of 'gravel's' (taking the letters G-R-A-V-E-L-S) = VERGLAS (thin ice coating, slippery stuff)