This muscle goes up and down and sends things round (7)
I believe the answer is:
rotator
'this muscle' is the definition.
(I've seen this before)
'up and down and sends things round' is the wordplay.
I cannot quite see how this works, but
'things' could be 'tat' (I have seen 'Tawdry things ' mean 'tat' so perhaps 'things' could also mean 'tat') and 'tat' is located in the answer.
'round' could be 'o' (o is a circular letter) and 'o' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'goes' acts as a link.
Can you help me to learn more?
(Other definitions for rotator that I've seen before include "It swivels" , "One goes round" , "Muscle that revolves a part of the body on its axis" , "One palindromic turner ..." , "Something that turns" .)