Possible Clues:

• Two-faced god of gates and doors - Guardian cryptic crossword setter
• Roman god depicted with two heads facing in opposite directions
• Two-faced Roman god who guarded doors and gates
• Roman god of doors, usually two-faced - a month is named for him
• -- -faced (duplicitous)
• Two-faced gatekeeper
• God for whom a month is named
• Two-faced Roman god - a month is named after him
• Two-faced Roman god of doors (5)
• See 68-Across