Arthurian knight causes great disturbance before the end of the skirmish (6)
I believe the answer is:
gareth
'arthurian knight' is the definition.
(I've seen this in another clue)
'great disturbance before the end of the skirmish' is the wordplay.
'great' becomes 'gare' (I am not sure about this - if you are sure you should believe this answer much more).
'disturbance' is an anagram indicator.
'before' means one lot of letters go next to another.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'end of the' says to take the final letters.
The last letter of 'skirmish' is 'h'.
't' put after 'h' is 'ht'.
'ht' with letters rearranged gives 'th'.
'gare'+'th'='GARETH'
'causes' is the link.
Can you help me to learn more?
(Other definitions for gareth that I've seen before include "Man's name" , "K" , "M. name; her tag (anag.)" , "-- Gates, UK singer" , "- - Edwards (rugby)" .)