Copper, say, finding corrupt mate turning liberal (4,5)
I believe the answer is:
base metal
'copper say' is the definition.
'base metal' can be an answer for 'copper' (I've seen this before). I am not sure about the 'say' bit.
'corrupt mate turning liberal' is the wordplay.
'corrupt' becomes 'base'.
'turning' is an anagram indicator.
'liberal' becomes 'l' (abbreviation).
'mate' with letters rearranged gives 'meta'.
'base'+'meta'+'l'='BASE METAL'
'finding' acts as a link.
Can you help me to learn more?
(Other definitions for base metal that I've seen before include "Say, iron" , "lead, perhaps" , "lead, say?" , "Lead, for example" , "Maybe lead" .)