Stone wrapped in Lycra -- broken quartz? (7)
I believe the answer is:
crystal
'quartz?' is the definition.
(quartz is a type of crystal)
'stone wrapped in lycra broken' is the wordplay.
'stone' becomes 'st'.
'wrapped in' indicates putting letters inside.
'broken' is an anagram indicator.
'lycra' with letters rearranged gives 'cryal'.
'st' put into 'cryal' is 'CRYSTAL'.
(Other definitions for crystal that I've seen before include "Regular-shaped mineral piece" , "Material of fortune-teller's ball" , "Quartz glass" , "Very clear glass" , "Glass made at Waterford" .)