Infant crab perhaps, one with turn of speed (6)
I believe the answer is:
nipper
'speed' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for nipper that I've seen before include "Infant (colloq.)" , "It may pinch" , "Small boy (old slang)" , "A pincer or a young boy" , "Large claw of a crab" .)