### Clue: Gas encountered – hydrogen and nitrogen in a mine with minute gone (7)
### Answer: METHANE 
 ### Explanation: Definition: Gas
 MET(encountered) + H(chemical symbol for the element hydrogen) + [ N(ditto for the element nitrogen) **contained in**(in) "a mine " **minus**(with … gone) "min"(short for "minute", 60 seconds) ].