Crossword Genius

Where to store documents from a long investigation involving Tibet's banks (7,4)

Ross

I believe the answer is:

attache case

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'where to store documents' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.

'a long investigation involving tibet's banks' is the wordplay.
'long' becomes 'ache' (to long for something is to ache for it).
'investigation' becomes 'case'.
'involving' indicates putting letters inside.
'banks' says to hollow out the word (remove centre letters) (the sides or banks of the word).
'tibet' with its middle removed is 'tt'.
'a'+'ache'+'case'='aachecase'
'aachecase' going around 'tt' is 'ATTACHE-CASE'.

'from' acts as a link.

Can you help me to learn more?

(Other definitions for attache case that I've seen before include "Carrier for documents, etc" , "Diplomatic incident" , "This is where documents may lie" , "Document carrier" , "Small briefcase" .)

I've seen this clue in The Times.
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