England, gutted, regularly mourned old king (6)
I believe the answer is:
edmund
'old king' is the definition.
(various medieval kings)
'england gutted regularly mourned' is the wordplay.
'gutted' says to hollow out the word (remove centre letters) (to gut something is to remove its insides).
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'england' with its middle taken out is 'ed'.
The alternating letters of 'mourned' are 'mund'.
'ed'+'mund'='EDMUND'
(Other definitions for edmund that I've seen before include "- Blunden; - Burke" , "- Ironside, English king" , "-- Hillary; -- Spenser" , "One of two kings of England, d. 946 and 1016, respectively" , "St. - - the Martyr" .)