The term REFRAIN PART can be broken down into three crossword solutions: TRA (3 letters), LALA (4 letters), and TRALA (5 letters). TRA is an abbreviation for the word 'TRANSPORT' and is commonly used in the context of transportation. LALA is a sound often used to represent singing or humming, and is often used in musical contexts. TRALA is a combination of the words 'tra' and 'lala', and is used to refer to a repeated phrase or section of a song. All three terms are related to music and can be used to describe a refrain part of a song.