Unexpected sound regularly upset Homer's neighbour (6)
I believe the answer is:
sudden
'unexpected' is the definition.
(similar in meaning)
'sound regularly upset homer's neighbour' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'upset homer's neighbour' becomes 'den' (I can't justify this - if you can you should believe this answer much more).
The alternate letters of 'sound' are 'sud'.
'sud'+'den'='SUDDEN'
Can you help me to learn more?
(Other definitions for sudden that I've seen before include "Done unexpectedly" , "Quick and unexpected" , "Happening quickly and without warning" , "Swift" , "'Unexpectedly, without warning (6)'" .)
