it will probably eat yur shrimp but it may leave the star alone. If u put it in just watch it closely and have another tank ready for the shrimp or trigger if they don't get along.
just reread this. If it is very small then you should be okay but still monitor it. also it could go either way. I have seen a cleaner shrimp clean a lion b4 so anything is possible in yur setup. how big is yur tank becauswe u need like a 75 gallon for a full grown trigger