Both Uses of

patron
in
The Great Gatsby

The fact was infinitely astonishing to him, and I recognized first the unusual quality of wonder, and then the man — it was the late patron of Gatsby's library.
p. 54.0

patron = person who was making use of

When he realized what I was talking about, that there were twinkle-bells of sunshine in the room, he smiled like a weather man, like an ecstatic patron of recurrent light, and repeated the news to Daisy.
p. 89.6 *

patron = supporter

Definitions:

(1) (patron as in: a patron of the arts)
a regular customer; or someone who gives money or support to an organization, cause, or person
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

In ancient Roman history, patron referred to the more powerful person in a complex client-patron relationship. The term is still used in some cultures today to describe a property owner who is in charge of workers.

Also see patron saint.

Much more rarely, a patron is the proprietor of an inn.