Related Clues:

• Sign up for the military
• Come into, as a room
• Key in, say
• Board a vehicle
• Cross a threshold
• Sign up for something
• Key often used to come in
• Come in from silent era
• Recruit in US army maybe, sent from Dallas, showing guts
• Doorman's invitation
• Ellen Terry's part to come on stage
• Go in with key
• Pass the jamb
• Join some dissenters
• Key that moves the cursor to the next line ... or a hint to answering five clues in this puzzle