Summit just too much for this climber? (3)
I believe the answer is:
pea
'this climber?' is the definition.
(the pea plant is a climbing plant)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for pea that I've seen before include "Vegetable in a whistle" , "registered by princess in bed" , "food item" , "Edible green seed" , "Tiny stone" .)