If i understood well, you code should look like this:
desc = []
with open('football.txt') as txt:
footballFixtures = [cut.strip().split(':') for cut in txt.readlines()]
print footballFixtures
for typeoffixture,descriptionoffixture,dateoffixture,resultoffixture in footballFixtures:
desc.append(descriptionoffixture)
first = StringVar()
first.set("Select a Fixture")
OptionMenu(root,first, *desc).place(x=90, y=150)