One hundred arms and legs — or shins? (6)
I believe the answer is:
climbs
'shins?' is the definition.
(shinning is a kind of climbing)
'one hundred arms and legs' is the wordplay.
'one hundred' becomes 'C' (Roman numeral).
'arms and legs' becomes 'limbs' (your limbs are your arms and legs).
'c'+'limbs'='CLIMBS'
'or' acts as a link.
(Other definitions for climbs that I've seen before include "Goes up" , "Ascends with difficulty" , "Advances" , "Ascends a hill or ladder" , "Moves upward slowly" .)