I've already mentioned before that you will have an opportunity to fulfill this task along with the other one. Once you've secured the MG nest, you will be able to proceed with this goal right away, so it's only going to take you 30-60 seconds to win. Nevertheless, you should be very careful here, because the plunger is going to be well defended by German soldiers.
Reaching your target:
I assume that you've started the game near the final heavy machine gun post. As a result, you will only have to turn right and make a few steps towards your new destination. The easiest way to get rid of the plunger would be to blow it up, so you should consider using at least one grenade here. Otherwise you would also have to kill 3-6 enemy soldiers. Either way, destroy the plunger and wait for some new objectives to be displayed on your screen.