Crack a nut and you can eat it (4)

I believe the answer is:

tuna

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'you can eat it' is the definition.
I can't tell whether this definition defines the answer.

'crack a nut' is the wordplay.
'crack' indicates anagramming the letters.
'a'+'nut'='anut'
'anut' is an anagram of 'TUNA'.

'and' acts as a link.

Can you help me to learn more?

(Other definitions for tuna that I've seen before include "Yellow-finned fish" , "Large sea-fish" , "Large food fish" , "Sea creature" , "Widely-eaten fish" .)

I've seen this clue in the Evening Standard.

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