Poet's author in ship with monarch (7)
I believe the answer is:
spenser
'poet's' is the definition.
(16th-century poet Edmund Spenser)
'author in ship with monarch' is the wordplay.
'author' becomes 'pen' (to pen something is to author it).
'in' is an insertion indicator.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'with' means one lot of letters go next to another.
'monarch' becomes 'er' (abbreviation for Elizabeth Regina, British Queen).
'pen' inserted inside 'ss' is 'spens'.
'spens'+'er'='SPENSER'
(Other definitions for spenser that I've seen before include "He wrote" , "English poet of 'The Faerie Queene'" , "Edmund - , sixteenth century English poet" , "Edmund -, Eng. poet" , "Old English poet" .)