### Clue: Flipping source of life is plague (7)
### Answer: NEMESIS 
 ### Explanation: Definition: plague
 **Reversal of**(Flipping, in a down clue) SEMEN(the source of life, strictly, the liquid medium for one half of the source of life, or is that being too technical) + IS.
Answer: Any agency of retribution, like what the plague was once considered to be.