Big bucks for song (7)

I believe the answer is:

fortune

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

'big bucks for song' is the definition.
I can't judge whether this definition defines the answer.

'for song' is the wordplay.
'song' becomes 'tune' (I've seen this before).
'for'+'tune'='FORTUNE'

Can you help me to learn more?

(Other definitions for fortune that I've seen before include "Great accumulation of wealth" , "A lot of money - luck" , "Fate; riches" , "Big bucks - fate" , "Providence" .)

I've seen this clue in The Sun.

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