Ranter straying like a knight? (6)
I believe the answer is:
errant
'a knight?' is the definition.
(a knight errant was a medieval wandering knight)
'ranter straying' is the wordplay.
'straying' indicates anagramming the letters.
'ranter' with letters rearranged gives 'ERRANT'.
'like' acts as a link.
(Other definitions for errant that I've seen before include "Straying; knight" , "Wrong" , "Wayward - ranter (anag)" , "Root vegetable" , "Wandering (as a knight?)" .)