The answer to your question would be that the underlined adverb that can also be used as a noun is the following one: Evenings.
Explanation:
Evening can also be used as a noun. This noun refers to "the period of time at the end of the day, usually from about 6 p.m to bedtime". For instance, you say "it was seven o'clock in the evening". As you can see, "evening" is acting as a noun as it is the head of the NP complement of the preposition "in".
