Arrived outside hospital with sick lone animal (9)
I believe the answer is:
chameleon
'animal' is the definition.
The answer is an example.
'arrived outside hospital with sick lone' is the wordplay.
'arrived' becomes 'came' (coming is a kind of arriving**).
'outside' means one lot of letters goes inside another.
'hospital' becomes 'h'.
'with' means one lot of letters go next to another.
'sick' indicates anagramming the letters.
'came' enclosing 'h' is 'chame'.
'lone' anagrammed gives 'leon'.
'chame'+'leon'='CHAMELEON'
(Other definitions for chameleon that I've seen before include "Lizard whose skin changes colour" , "One to blend in" , "colour changer" , "Lizard that can change colour to match surroundings" , "Person who keeps changing" .)