Poet hired assassin to follow wife (7)
I believe the answer is:
whitman
'poet' is the definition.
(I've seen this before)
'hired assassin to follow wife' is the wordplay.
'hired assassin' becomes 'hit man' (I've seen this before).
'to follow' means one lot of letters go next to another.
'wife' becomes 'w'.
'hitman' after 'w' is 'WHITMAN'.
(Other definitions for whitman that I've seen before include "American writer" , "Walt . . . . . . . great American poet" , "Slim < country and western singer" , "Walt --, US poet" , "Walt . . . . . . ., American poet of 'Leaves of Grass'" .)