Possible Clues:

• Skilled craftsman
• Mechanic making a terrific mess
• Craftsman's erratic if disturbed
• "Steel-true and blade-straight / The great –– / Made my mate" (Stevenson)
• One who contrives to be a naval mechanic
• Shaw briefly a captain, for example, but not of this skilful soldier
• A terrific construction worker
• Forces mechanic to make a terrific explosion
• Mechanic extracting some part if ice recedes
• Deception beginning to repel army mechanic