Move restlessly, following unintroduced thingamyjig (6)
I believe the answer is:
fidget
'move restlessly' is the definition.
(synonyms)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for fidget that I've seen before include "Make small restless movements with hands" , "Betray boredom, impatience" , "Move restlessly" , "Squirm" , "person always on the move" .)