Weird mineral reduced in mass (4)
I believe the answer is:
eery
'weird' is the definition.
(I've seen this in another clue)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for eery that I've seen before include "Spooky" , "Weird" , "Weirdly frightening" , "Strange" , "Strangely frightening" .)