Good old Bluth's highly profitable venture? (4,4)

I believe the answer is:

gold mine

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'highly profitable venture?' is the definition.
The definition suggests a singular noun which matches the answer.

'good old bluth's' is the wordplay.
'good' becomes 'g' (abbreviation).
'bluth's' becomes 'mine' (where the crossword setter is 'Bluth').
'g'+'old'+'mine'='GOLD-MINE'

Can you help me to learn more?

(Other definitions for gold mine that I've seen before include "Source of great wealth" , "Source of great riches" .)

I've seen this clue in The Independent.

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