Detroit NBAer (6)
I believe the answer is:
piston
'detroit nbaer' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for piston that I've seen before include "Block sliding in hollow cylinder in machinery etc" , "Mechanical plunger" , "Points about driving rod" , "Driving rod in engine" , "Mechanical device that has a thrusting motion" .)