### Clue: Christian starting off with a measure of whisky? (5)
### Answer: OPTIC 
 ### Explanation: Definition: a measure of whisky?
A subtraction: [c]OPTIC ('Christian', principally in Egypt) minus the first letter ('starting off'). An OPTIC is the device attached to an inverted bottle to measure a standard amount of a spirit, with the question mark for whisky as an example.