The answer is a number

[crachet]

1. Earliest date seven disparate Romans can make. (4)
2. Regular remedy for a major blockage. {1)
3. Disabled U.S.A. spyshot dead in February. (3)
4. Bobby Fischer's opening moves, possibly. (2)
5. How many study outside Australia? (2)

[gen2]

5. Dozen = 12 (Oz inside DEN)

[Dimbo]

mdclxvi = 1666

[crachet]

Thank you both for your help. Crachet

[lesblue]

3. 193

http://en.wikipedia.org/wiki/USA_193

[crachet]

Thank you lesblue. I was going mad trying to associate the question with a human spy! Crachet.

[alcibiades]

for 1 why not mcdxliv 1444 ?

[crachet]

Thanks alcibiades. Eventually all the answers add up to a certain figure, so I shoud be able to arrive at the required date by elimination.