Little creature allowed outside always (7)
I believe the answer is:
leveret
'little creature' is the definition.
(young hare)
'allowed outside always' is the wordplay.
'allowed' becomes 'let' (to let is to allow or permit).
'outside' means one lot of letters goes inside another.
'always' becomes 'ever' (synonyms).
'let' enclosing 'ever' is 'LEVERET'.
(Other definitions for leveret that I've seen before include "Young animal" , "Speedy young thing" , "Young hare" , "Small hopper" , "First-year hare" .)