Animal last to leave country (5)
I believe the answer is:
eland
'animal' is the definition.
(thesaurus)
'last to leave country' is the wordplay.
'last to' indicates one should take the final letters.
'country' becomes 'land' ('land' can be a synonym of 'country').
The final letter of 'leave' is 'e'.
'e'+'land'='ELAND'
(Other definitions for eland that I've seen before include "Spiral-horn antelope" , "Large spiral-horned African antelope" , "Wild beast" , "Browser" , "Large African deer with short spiral horns" .)