Stone encountered in hasty scramble (8)
I believe the answer is:
amethyst
'stone' is the definition.
(I've seen this before)
'encountered in hasty scramble' is the wordplay.
'encountered' becomes 'met' ('meet' can be a synonym of 'encounter').
'in' means one lot of letters goes inside another.
'scramble' indicates an anagram.
'hasty' anagrammed gives 'ahyst'.
'met' going within 'ahyst' is 'AMETHYST'.
(Other definitions for amethyst that I've seen before include "One showing sparkling facets" , "Something precious" , "what's in ring" , "Precious stone of purple quartz" , "Variety of quartz" .)