Lithium twisted inside small piece of metal (6)

I believe the answer is:

silver

I'm a little stuck... Click here to teach me more about this clue!

'lithium' is the definition.
(thesaurus)

'twisted inside small piece of metal' is the wordplay.
'twisted' is a reversal indicator.
'inside' says to take the centre.
'small' becomes 'derisory'.
'piece of metal' becomes 'lver' (I am not sure about this - if you are sure you should believe this answer much more).
The middle letters of 'derisory' are 'is'.
'is' back-to-front is 'si'.
'si'+'lver'='SILVER'

Can you help me to learn more?

(Other definitions for silver that I've seen before include "Pirate" , "treasure" , "Change - Ag" , "Precious metal, Ag" , "Movies" .)

I've seen this clue in The Guardian.

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