Acelas

3 clues
Amtrak speedsters
Some express trains
Some high-speed trains
Similar answers:
Aaacell
Aacell
Aacells
Aattheraces
Abankisaplace
Ablast
Ablastingindisguise
Aboutface
Aboutfaced
Aboutfaceoff
Aboutlastnight
Abovethesurface
Abraceofbirds
Abraceofdentists
Accountofrace
Ace
Acea
Aceae
Aceaward
Acebandage