Like many a sniper, 4 letters
Foreword, 5 letters
Intro, 5 letters
Introducion to a book, 5 letters
Introduction, 5 letters
Introduction or preface, 5 letters
Introductory discourse, 5 letters
Preamble, 5 letters
Preface, 5 letters
Prelude, 5 letters
Short introduction, 5 letters
Book prefaces, 6 letters
Forewords, 6 letters
Introductions, 6 letters
Introductory discourses, 6 letters
Preliminary comments, 6 letters
CSI: Miami actress Emily, 5 letters
Any of a group of compounds that are inactive precursors of enzymes and require some change (such as the hydrolysis of a fragment that masks an active enzyme) to become active, 9 letters