One rare element still emptied with another (9)
I believe the answer is:
ytterbium
'one rare element' is the definition.
'ytterbium' can be an answer for 'element' (ytterbium is a kind of element). I am not sure about the 'one rare' bit.
'still emptied with another' is the wordplay.
'still' becomes 'yet' (synonyms).
'emptied' means to remove the middle letters.
'with another' becomes 'terbium' (I can't justify this - if you can you should give a lot more credence to this answer).
'yet' with its centre removed is 'yt'.
'yt'+'terbium'='YTTERBIUM'
Can you help me to learn more?
(Other definitions for ytterbium that I've seen before include "metal" , "Rare-earth element" , "Atomic number 70" , "SEVENTY" , "Element with symbol Yb" .)