Sound of hooter round middle of shift (5)
I believe the answer is:
noise
'sound' is the definition.
(a noise is a sound)
'hooter round middle of shift' is the wordplay.
'hooter' becomes 'nose' (I've seen this before).
'round' is an insertion indicator.
'middle of shift' becomes 'i' (I am not sure about this - if you are sure you should believe this answer much more).
'nose' placed around 'i' is 'NOISE'.
'of' is the link.
Can you help me to learn more?
(Other definitions for noise that I've seen before include "Unpleasant sounds" , "Unwanted sound" , "explosive report, for example" , "Rumour" , "Din, cacophony" .)