Related Clues:

• Allowing only a single direction
• Not allowing reverse motion
• Perhaps unrequited love experienced for the first time, yes?
• Unfairly biased
• Revolutionary ace in utterance to grab attention permitting no U-turn
• Like non-return valve
• Not allowing return motion
• Grossly unequal
• Allowing motion in a single direction
• Biased, unfair
• Allowing no return movement
• Indeed so flipping unfair
• Not even I camp on first of December!
• Traffic sign with an arrow
• Partisan