Do you or your partner make a habit of opening light when you are in the third seat?
If the answer is 'No', then go to another Convention, this one is of no use to you.

But if you do frequently deal with the possibility that the third seat 1-of-a-Major-suit opening may be only 10 or 11 points then you know what a problem it can be for the partner who originally passed with 12 points. She won't know whether to start jumping to game, or to tread more lightly.

Reverse Drury is a convention designed solely to allow the partner to find out whether that opening bid is full-strength or not.

Suppose the third seat opening bid is 1♠, and you have good trump help with 12 points.
You bid 2♣. This is Reverse Drury and has nothing to do with a ♣ suit.
If the Opening was light, the Opener just returns to 2♠, and you would of course pass.
If the Opening was full-strength, the Opener usually bids 2, after which you jump to 3 or 4 ♠.

Reverse Drury is only used after Major suit openings in third seat.
By the way, it is called REVERSE Drury because the original convention used 2 to show a light opening and a return to the Major to show a full-strength one.

Lesson available.