Small rodents returning in animal enclosure, for example (8)
I believe the answer is:
specimen
'example' is the definition.
(specimen is a kind of example)
'small rodents returning in animal enclosure' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'rodents' becomes 'mice' (mouse is a kind of rodent).
'returning' says the letters should be written backwards.
'in' indicates putting letters inside.
'animal enclosure' becomes 'pen' (I've seen this before).
'mice' in reverse letter order is 'ecim'.
'ecim' placed within 'pen' is 'pecimen'.
's'+'pecimen'='SPECIMEN'
'for' acts as a link.
(Other definitions for specimen that I've seen before include "Copy" , "Representative sample" , "Derogatory description of person" , "Test sample" , "Part taken as example of whole or class" .)