One word substitution:

1.Allowance due to a wife from her husband on separation - Alimony
2.Belonging to all parts of the world - Universal
3.Words of similar meaning - Synonyms
4.A speech delivered without previous preparation - Extempore
5.Study of heavenly bodies - Astronomy
6.To cut apart a person’s body - Mutilate
7.One who is filled with excessive and mistaken enthusiasm about his religion -Fanatic
8.An involuntary action under a stimulus is described as a - Reflex
9.The use of many words where only a few are necessary - Circumlocution
10.One who is a citizen not of a country but of the world - Cosmopolitan
11.An imaginary name assumed by an author for disguise - Pseudonym