Possible Clues:

• Sun might upset one who's up in arms?
• Smug hint (anag)
• One makes or sells weapons
• Weapons maker
• One works with lifeless arms
• Firearms maker/dealer
• One makes or sells small firearms
• Pistol maker
• Heartless man is thug, horrible person with weapons
• Causes of death at foreign university hospital responsible for the emergence of 2 down