Landor could be an English poet (6)
I believe the answer is:
arnold
'an english poet' is the definition.
(19th-century poet Matthew Arnold)
'landor could be' is the wordplay.
'could be' is an anagram indicator.
'landor' with letters rearranged gives 'ARNOLD'.
(Other definitions for arnold that I've seen before include "Overcome (obstacle)" , "Sir Malcolm -, composer (Bridge over the River Kwai)" , "Sir Malcolm -, English composer" , "Essayist" , "Matthew --; -- Bennett" .)