If there are no hazards or substitutes will Tidy Up still grant an attack and speed boost?
Tidy Up raises the user's Attack stat and Speed stat by one stage each. It also clears away substitutes, Spikes, Toxic Spikes, Stealth Rock, and Sticky Web on both the user's and target's side of the field. The user's stats will still be raised even if there are no traps or substitutes to remove.
Source
No, the move will not fail, and will still provide the attack and speed boost.
Hope I could help!
Tidy Up will still raise the user's attack and speed.
Maushold used Tidy Up! Maushold's Attack rose! Maushold's Speed rose!
Also, I tested it in-game and Maushold's Attack and Speed rose, even though there were no hazards.