I can do it IF you know whether the fake is heavier or lighter in advance, but I'm really struggling with it as it is.....

For example, if you knew the fake was heavier:

Divide into 3 x 4 called G1, G2 and G3

Weigh G1 against G2. Either the heavier of those two contains the fake or, if the same then G3 contains the fake.

Take 2 coins from a known 'good' pile and measure against two from the 'fake' pile. If they match, the remaining two have the fake, or you will identify the fake as being the heavier one on the balances.

Do the same again with one good against one of the 'fake' pair and voila.

But, say you get the fake one of the sets on the scales in the first step, and you don't know if its heavier or lighter, then you're stuck without doing extra weighings.