The term 'ONE OF A MATCHING PAIR' can be broken down into three separate crossword solutions: HERS (4 letters), HIS (3 letters), and TWIN (4 letters). HERS is a possessive pronoun used to refer to a female, while HIS is a possessive pronoun used to refer to a male. TWIN is a noun that refers to two people or things that are the same in almost every way. Together, these three solutions form the phrase 'ONE OF A MATCHING PAIR', which is used to describe two people or things that are similar in many ways.