Stone making them stay (8)
I believe the answer is:
amethyst
'stone' is the definition.
(I've seen this before)
'making them stay' is the wordplay.
'making' indicates anagramming the letters.
'them'+'stay'='themstay'
'themstay' anagrammed gives 'AMETHYST'.
(Other definitions for amethyst that I've seen before include "Transparent bluish quartz" , "Purple quartz, used as a gemstone" , "Something precious" , "Violet-coloured stone" , "Purple quartz used in jewellery" .)