Huge volume on duke misused key, valuable source (8)

I believe the answer is:

klondyke

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'valuable source' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'huge volume on duke misused key' is the wordplay.
'huge volume' becomes 'kl' (I can't explain this - if you can you should believe this answer much more).
'duke' becomes 'd' (abbreviation).
'misused' indicates anagramming the letters.
'key' is an anagram of 'yke'.
'kl'+'on'+'d'+'yke'='KLONDYKE'

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I've seen this clue in The Times.

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