Regularly assaulted somewhere in Greater Manchester (4)
I believe the answer is:
sale
'somewhere in greater manchester' is the definition.
(I know that Sale is in Greater Manchester)
'regularly assaulted' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternating letters of 'assaulted' are 'SALE'.
(Other definitions for sale that I've seen before include "Period of reduced prices" , "Auction - somewhere in Greater Manchester" , "Auction; Cheshire town" , "Retail event - town in Greater Manchester" , "Period of low prices" .)