Get round a wide knight (6)
I believe the answer is:
gawain
'knight' is the definition.
(I know this)
'get round a wide' is the wordplay.
'get' becomes 'gain' (gaining is a kind of getting).
'round' indicates putting letters inside.
'wide' becomes 'w' (abbreviation e.g. in cricket).
'a'+'w'='aw'
'gain' going around 'aw' is 'GAWAIN'.
(Other definitions for gawain that I've seen before include "K" , "round a table for him and his comrades?" , "Arthurian knight of the Round Table" , "One of King Arthur's knights" , "Man at round table" .)