It is part of the game to open a little light in 3rd seat.  The Drury convention is an attempt to cater for that when supporting partner with a passed hand.

Opposite a 3rd/4th seat opening in a Major a 2♣ response is artificial showing a constructive raise of openers suit (i.e. 1♥,3♥ type of support).  Opener re-bids 2♦ with a minimum hand or one that would not consider game.  Responder then signs off in two of the Major.  Any other bid by opener is natural and shows a sound opening, with interest in game.

There is debate over the usefulness of Drury against strong players - is it that clever to tell opponents that you have a fit and limited values?  It might tell them that they can compete and push you to an awkward level.