The sentence you wrote is almost perfect! Let's look at it carefully.
Original sentence: A weaver loops grass and twigs to make its light nest.
The grammar is correct. The sentence is clear and makes sense. It tells us what a weaver does using grass and twigs.
One tiny suggestion: you might consider adding a little word to make it sound smoother, like "a light nest" instead of "its light nest" if you mean any light nest in general, or keep "its" if you want to emphasize the nest belongs to the weaver.
So both of these are correct:
- A weaver loops grass and twigs to make a light nest.
- A weaver loops grass and twigs to make its light nest.
Great job writing this sentence!