Clown triggers get quite large, your going to need a bigger tank to keep this beautiful fish long term. What else do you have in the tank? These fish have a high likelyhood of showing very aggresive behaviour so much caution is needed.
From reading and experience, these fish can turn tempermentally on a dime, acting quite normal with your picasso for some time, then picking his teeth with him in a moments notice.
If it is a Juvenile Clown Trigger, you have more time but they have very high mortality rates (low survivability chances.)
Hope this helps!