The term 'obstacle to progress' can be summarized by two crossword solutions: INERTIA (7 letters) and LOGJAM (6 letters). INERTIA is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to remain at rest or in motion. LOGJAM is a situation in which a process or activity is hindered or blocked due to a large number of people or things involved. Both terms refer to a situation in which progress is hindered or blocked due to a lack of action or movement.