Formerly large case (7)

I believe the answer is:

example

'case' is the definition.
(thesaurus)

'formerly large' is the wordplay.
'formerly' becomes 'ex'.
'large' becomes 'ample' ('ample' can be similar in meaning to 'large').
'ex'+'ample'='EXAMPLE'

(Other definitions for example that I've seen before include "Instance, specimen" , "Characteristic item" , "Illustrative exercise" , "Typical specimen" , "not the actual version" .)

I've seen this clue in The Times.

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