That's out of my area of study.
My older sister is a specialty pet eye doctor.
My specialty is astronomy. I want to discover new stars.
Your specialty gate is the thing you open to let out your specialty. Imagine the thing you're best at (your specialty). Now imagine opening a gate in your chest that lets it out, allowing you to be good at it.
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.