Specimen is no longer enough (7)
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I believe the answer is:
example
'specimen' is the definition.
(I've seen this in another clue)
'no longer enough' is the wordplay.
'no longer' becomes 'ex' (prefix meaning former or onetime).
'enough' becomes 'ample' (ample means enough or plenty).
'ex'+'ample'='EXAMPLE'
'is' acts as a link.
(Other definitions for example that I've seen before include "Illustrative exercise" , "Paradigm or model" , "Illustration or model" , "Model - instance" , "Standard" .)