### Clue: Oxygen coming in a little lower, excellent source of fuel (8)
### Answer: COALFACE 
 ### Explanation: Definition: source of fuel
 O(symbol for the chemical element, oxygen) **contained in**(coming in) [ CALF(a little/a young bovine animal, a low-er/one that would low/moo) + ACE(slang for excellent/very good) ].
Defn: Part of a mine with exposed coal.