Related Clues:

• Carriage return key, nowadays
• Sign up to compete
• Go in and put in the ledger
• Come in or record
• Come or go in
• Enroll, sign up
• Go or come in
• Twenty-first letter of the Greek alphabet
• Enlist, join up
• What the fish might do to get in like this under it for 18 down
• Do not go away before it is trouble inside
• Saw what the carp might be doing with this
• One thus won't go and prise such an undertaking
• After this it is trouble inside when you come in
• Sounds as if this might get the prize for initiative