noun, の adjective
You know that 旅行 is a trip. The other part is new marriage. What's the trip you go on after a new marriage? The honeymoon!
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
I can’t wait to go to Hawaii for my honeymoon! Yen is high, so I’m going to spend all my money on shopping. Haha.