Mats they removed to find gem (8)
I believe the answer is:
amethyst
'gem' is the definition.
(amethyst is a kind of gem)
'mats they removed' is the wordplay.
'removed' is an anagram indicator (moved again).
'mats'+'they'='matsthey'
'matsthey' is an anagram of 'AMETHYST'.
'to find' acts as a link.
(Other definitions for amethyst that I've seen before include "February gemstone" , "Purple quartz used in jewellery" , "Bluish-violet 3" , "Transparent bluish quartz" , "Variety of quartz" .)