The term 'COLLECTOR's QUEST' can be broken down into two words, 'COLLECTOR' and 'QUEST'. A COLLECTOR is someone who collects items of interest, such as coins, stamps, or antiques. A QUEST is an adventurous journey or mission to find something. Therefore, a COLLECTOR's QUEST is a mission to find rare items of interest. The crossword solutions for this term are SET (3 letters) and RARESPECIMEN (12 letters). SET is a verb meaning to put in order or arrange systematically. RARESPECIMEN is a noun meaning an unusual or uncommon example of something. Together, these two words describe the mission of a COLLECTOR's QUEST: to arrange and find rare items.