Crossword Genius

Shape up to buy a suitcase (3,1,4)

Ross

I believe the answer is:

get a grip

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'shape up' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'buy a suitcase' is the wordplay.
'buy' becomes 'get' (both can mean to purchase or obtain).
'suitcase' becomes 'grip' (synonyms).
'get'+'a'+'grip'='GET A GRIP'

'to' is the link.

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I've seen this clue in The Times.
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