Letters from London nearly delivered for poet (5)
I believe the answer is:
donne
'for poet' is the definition.
(16th- and 17th- century poet John Donne)
'letters from london nearly delivered' is the wordplay.
'letters from' indicates the answer is hidden within the clue (a selection of letters from the clue).
'DONNE' is hidden within 'london nearly delivered'.
(Other definitions for donne that I've seen before include "basic assumption" , "John -, English poet" , "English preacher and metaphysical poet, d. 1631" , "Writer of poetry" .)