Rubbish outside of our bit of machinery (5)
I believe the answer is:
rotor
'bit of machinery' is the definition.
'rotor' can be an answer for 'machinery' (I have seen 'Revolving machinery ' mean 'rotor' so perhaps 'machinery' could also mean 'rotor'). I'm not sure about the 'bit of' bit.
'rubbish outside of our' is the wordplay.
'rubbish' becomes 'rot' (both can mean nonsense).
'outside of' says to hollow out the word (remove centre letters).
'our' with its middle removed is 'or'.
'rot'+'or'='ROTOR'
Can you help me to learn more?
(Other definitions for rotor that I've seen before include "Device to propel a helicopter" , "Palindromic moving part" , "Spinner" , "Part of engine that revolves" , "Turning part of machine, palindromic" .)