Army section sound busy – I agree to return (7)
I believe the answer is:
humerus
'return' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'army section sound busy i agree' is the wordplay.
I cannot quite see how this works, but
'section' could be 's' (legal abbreviation) and 's' is found in the answer.
'sound' could be 'hum' (hum is a kind of sound) and 'hum' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'to' is the link.
Can you help me to learn more?
(Other definitions for humerus that I've seen before include "Upper arm bone" , "Upper-arm bone" , "Arm bone (that sounds comical)" , "What's often thought funny" , "Bone from shoulder to elbow" .)