Tree feline with mountain gorilla, finally (7)
I believe the answer is:
catalpa
'tree' is the definition.
(catalpa is a kind of tree)
'feline with mountain gorilla finally' is the wordplay.
'feline' becomes 'cat' (cat is a kind of feline).
'with' says to put letters next to each other.
'mountain' becomes 'alp' (the Alps are a mountain range).
'finally' says to take the final letters.
The last letter of 'gorilla' is 'a'.
'cat'+'alp'+'a'='CATALPA'
(Other definitions for catalpa that I've seen before include "Tree with heart-shaped leaves" , "it blossoms" , "A pal cat found in the American tree" .)