English country gent bites tail off rather large rodent (8)
I believe the answer is:
squirrel
'rodent' is the definition.
(squirrel is a kind of rodent)
'english country gent bites tail off rather large' is the wordplay.
'english country gent' becomes 'squire'.
'bites' indicates putting letters inside.
'tail off' suggests the final letters.
'large' becomes 'l'.
The final letter of 'rather' is 'r'.
'squire' going around 'r' is 'squirre'.
'squirre'+'l'='SQUIRREL'
(Other definitions for squirrel that I've seen before include "Grey or (rarely) red woodland creature" , "Brown or red rodent" , "Bushy-tailed rodent" , "Arboreal creature" , "Arboreal rodent with long bushy tail" .)