Your puzzle is solving a nested analogy, where the goal is to find the word that fills in the final blank, based on the answer to the analogy in parentheses.
An example:
sky:blue::(bird:worm::cow:____):____
In this case, the answer to the part in parentheses is "grass", which makes the whole thing:
sky:blue::grass:____
So, the final answer is green.
Now, for the puzzle you must solve (which is not as straightforward as the example):
wing:horn::(toodle-oo:hour::oboe:____):____