linchpin /linchˈ or linshˈpin/

1. A pin used to keep a wheel on its axle
2. A person or thing essential to a plan, organization, etc (figurative)

• wheel ploughs
• wheel race
• wheel races
• wheels
• wheelsman
• wheel spin
• wheel spins
• wheels within wheels
• wheel window
• wheel windows
• wheelwork
• wheelworks
• wheelwright
• wheelwrights
• wheely
• wheen
• wheenge
• wheenged
• wheenges
• wheenging
• wheens
• wheeple
• wheepled
• wheeples
• wheepling