Specimen from Devon river with no tail large enough (7)
I believe the answer is:
example
'specimen' is the definition.
(I know that specimen can be written as example)
'devon river with no tail large enough' is the wordplay.
'devon river' becomes 'exe' (I've seen this in another clue).
'with no tail' means to remove the last letter.
'large enough' becomes 'ample' (I've seen this before).
'exe' with its final letter taken away is 'ex'.
'ex'+'ample'='EXAMPLE'
'from' is the link.
(Other definitions for example that I've seen before include "Ideal - specimen" , "Standard" , "Thing illustrating a general rule" , "Typical specimen" , "Illustration or model" .)