### Clue: Brace used to help the spine, when oxygen is in short supply (8)
### Answer: ORTHOSIS 
 ### Explanation: Definition: Brace used to help the spine
 O(symbol for the element, oxygen) + **anagram of**(… supply;in a supple way, similar to "humbly") [IS **contained in**(in) SHORT].
I'm not satisfied with the explanation of "in".