The term 'collar insert' refers to a type of clothing accessory. It is typically a piece of fabric or other material that is inserted into the collar of a shirt or blouse to give it a more finished look. The two crossword solutions for this term are 'STUD' and 'STAY'. A STUD is a small, decorative item that is often used to fasten collars, while a STAY is a stiffening strip that is inserted into the collar to help keep its shape. Both of these items can be used as part of a collar insert to give a shirt or blouse a more polished appearance.