Acrimony without end unsettled inventor (7)
I believe the answer is:
marconi
'inventor' is the definition.
(I've seen this before)
'acrimony without end unsettled' is the wordplay.
'without end' means to remove the last letter.
'unsettled' indicates anagramming the letters.
'acrimony' with its final letter taken off is 'acrimon'.
'acrimon' is an anagram of 'MARCONI'.
(Other definitions for marconi that I've seen before include "The father of radio" , "Inventor of radio-telegraphy" , "Italian electrical engineer, d. 1937" , "Italian physicist" , "Communications pioneer" .)