This moves around, but to no effect? (7)
I believe the answer is:
rotator
'this moves around' is the definition.
The definition suggests a singular noun which matches the answer.
'to no effect?' is the wordplay.
I cannot quite see how this works, but
'to' is found in the answer.
'no' could be 'o' (O resembles 0) and 'o' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'but' is the link.
Can you help me to learn more?
(Other definitions for rotator that I've seen before include "Something that turns" , "Something turning" , "Muscle that turns" , "It swivels" , "One palindromic turner ..." .)