Old king chewing nut, making inarticulate sound (5)
I believe the answer is:
grunt
'inarticulate sound' is the definition.
(I've seen this before)
'old king chewing nut' is the wordplay.
'old king' becomes 'GR' (Georgius Rex, Latin for King George).
'chewing' indicates anagramming the letters.
'nut' is an anagram of 'unt'.
'gr'+'unt'='GRUNT'
'making' is the link.
(Other definitions for grunt that I've seen before include "Sound made by a pig" , "Oink" , "(Make the) sound of a pig" , "Inarticulate sound" , "Noise of a pig ..." .)