Mate’s reels sampled your old Deep Purple (8)
I believe the answer is:
amethyst
'purple' is the definition.
(thesaurus)
'mate's reels sampled your old deep' is the wordplay.
I cannot quite understand how this works, but
'your' could be 'thy' ('thy' historically meant 'your') and 'thy' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for amethyst that I've seen before include "February gemstone" , "Semiprecious stone of violet or purple quartz" , "Bluish-violet 3" , "Purplish gemstone" , "Violet-coloured stone" .)