Just want to add a little something :
مكثفة is an adjective (I think it's clear, just making sure it is)
The other word الحيلولة is always used as a whole expression الحيلولة دون. And its meaning was given already by Ayed.
the ل at the begining of الحيلولة means (to), we call it in arabic لام التعليل which means it comes in the sentence to explain the reason of the action.