Treble Chance .

[swannbaker]

Where , in France , three quarters of the army is wiped out . (8)

[atoach]

is (8) the number of letters ?
cos there's a place in France called Y, whch is what you get if you 'wipe out' 3/4 of the letters of 'army'.
sorry if i'm up the wrong tree.

[swannbaker]

8 is the number of letters and your thinking is in the right direction .