Specimen is old and adequate (7)
I believe the answer is:
example
'specimen' is the definition.
(I've seen this in another clue)
'old and adequate' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'and' says to put letters next to each other.
'adequate' becomes 'ample' (I've seen this in another clue).
'ex'+'ample'='EXAMPLE'
'is' is the link.
(Other definitions for example that I've seen before include "Punishment" , "Specimen, sample" , "Characteristic item" , "Case in point" , "Thing illustrating a general rule" .)