Both Uses of

obstruct
in
Utopia, by Thomas More

But they look upon those delights which men by a foolish, though common, mistake call pleasure, as if they could change as easily the nature of things as the use of words, as things that greatly obstruct their real happiness, instead of advancing it, because they so entirely possess the minds of those that are once captivated by them with a false notion of pleasure that there is no room left for pleasures of a truer or purer kind.†
*

obstruct = block or interfere

and that, if it had been distributed among them, none would have felt the terrible effects of that scarcity: so easy a thing would it be to supply all the necessities of life, if that blessed thing called money, which is pretended to be invented for procuring them was not really the only thing that obstructed their being procured!†

obstructed = blocked or interfered

Definition:

to block, slow down, or interfere with movement, progress, or action

The exact meaning of obstruct can depend upon its context. For example: