The term 'Be a Thorn' can be broken down into three crossword solutions: PAW (3 letters), PRICKED (7 letters), and STEM (4 letters). The phrase 'Be a Thorn' is an idiom that means to cause trouble or annoyance. To 'PAW' something is to touch it with the hands, claws, or hooves. To be 'pricked' is to be pierced or jabbed with a sharp object. A 'STEM' is the main stalk of a plant. Therefore, the phrase 'Be a Thorn' can be interpreted as touching someone or something with a sharp object in order to cause trouble or annoyance.