This achievement is for Rallycross - the Joker is the "extra" bit of the track that everyone has to drive along once in a race.
It's random as to whether this will be said, but before some events (for example if you're starting as the furthest left on Lydden Hill), the voiceover will say "you're in the optimal position to take the Joker immediately".
When this happens, if you can take the Joker and win the race the achievement should pop.
So far, I've only had this be said once to me in multiple races, even when I've started in the same place on the grid - and I lost that race - so there seems to be some element of randomness as to whether you will even get the prompt.