American poet has time to pen final letter (4)
I believe the answer is:
ezra
'american poet' is the definition.
(poet Ezra Pound)
'time to pen final letter' is the wordplay.
'time' becomes 'era' (era is a kind of time).
'to pen' is an insertion indicator.
'final letter' becomes 'Z'.
'era' enclosing 'z' is 'EZRA'.
'has' is the link.
(Other definitions for ezra that I've seen before include "Book after II Chronicles" , "Old Testament book and rabbi" , "... Pound, American poet who lived in Italy" , "Old Testament prophet" , "Old Testament book and priest" .)