Remain agitated with large copper? (7)
I believe the answer is:
mineral
'copper?' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'remain agitated with large' is the wordplay.
'agitated with' indicates anagramming the letters.
'large' becomes 'L' (eg in clothes sizes).
'remain' anagrammed with 'l' gives 'MINERAL'.
Can you help me to learn more?
(Other definitions for mineral that I've seen before include "Substance that is (usually) inorganic" , "ore, possibly" , "Substance needed for health; ore" , "What drink is available in ground" , "E.g. bauxite, quartz" .)