Example of rodents running back in not quite exhausted (8)

I believe the answer is:
specimen
'example' is the definition.
(specimen is a kind of example)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for specimen that I've seen before include "Example regarded as typical of its class" , "Derogatory description of person" , "Exemplar" , "Sample to be studied" , "Example of type" .)
