Creature takes rubbish outside lair (6)
I believe the answer is:
rodent
'creature' is the definition.
(rodent is a kind of animal)
'rubbish outside lair' is the wordplay.
'rubbish' becomes 'rot' (both can mean nonsense).
'outside' indicates putting letters inside.
'lair' becomes 'den' (synonyms).
'rot' going around 'den' is 'RODENT'.
'takes' is the link.
(Other definitions for rodent that I've seen before include "Eg, capybara" , "Mouse maybe" , "Small gnawing animal" , "A rat, for instance" , "Gnawing creature" .)