A large enclosure with standard support for climber (10)
I believe the answer is:
alpenstock
'support for climber' is the definition.
(stick used by a mountain climber)
'a large enclosure with standard' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'enclosure' becomes 'pen' (pen is a kind of enclosure).
'with' says to put letters next to each other.
'standard' becomes 'stock' (synonyms).
'a'+'l'+'pen'+'stock'='ALPENSTOCK'
(Other definitions for alpenstock that I've seen before include "Stick with a metal point, used by hillwalkers" , "Mountain climber's staff with a metal point" , "Metal-tipped mountaineering stick" , "climbing equipment" .)