The term context clue refers to the use of the words that surround an unknown word or expression to determine the meaning of the unknown section, this usually implies the words in a text suggest or provide hints about the meaning that helps the reader understand difficult words. Additionally, context clues can appear in the same sentence or even in the next sentence. In the passage presented the expression that unknown is "snowy Kilimanjaro" which refers to the mount Kilimanjaro the highest mount in Africa that is covered by snow as in this case the author compares this mount the amount of snow that is over the car.
In this case, the meaning of the unknown section is suggested by the expression "I went to get a shovel" as this shows the narrator needs a shovel to "recover" the car and therefore the element that has transformed the car into the "Kilimanjaro" was the snow accumulated over it. Thus the clue that best helps the reader understand the meaning of "snowy Kilimanjaro" is "I went to get a shovel" because this makes the reader understand the car has been covered by a huge amount of snow that makes it look like a huge mountain covered by snow and because of this the narrator needs a shovel to recover the car.