The term 'shot in the arm' is a metaphor for something that provides a sudden, positive change or improvement. The crossword solutions for this term are TONIC (5 letters), LIFT (4 letters), HYPO (4 letters), AMMO (4 letters), BOOST (5 letters), and EGOBOOST (8 letters). A TONIC is a medicinal drink that is believed to have health benefits. A LIFT is an act of raising or increasing something. A hypo is a hypodermic needle, which is used to inject medicine into the body. AMMO is short for ammunition, which is a type of weapon. BOOST is an increase in power or energy. An ego BOOST is a feeling of increased self-confidence or self-esteem.