Tall mammal (7)
I believe the answer is:
giraffe
'tall mammal' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for giraffe that I've seen before include "A long-legged creature" , "Tall quadruped" , "Tallest living quadruped" , "Long-necked ruminant" , "Long-necked browser" .)