Poet in with Romeo (5)
I believe the answer is:
homer
'poet' is the definition.
(Homer is an example)
'in with romeo' is the wordplay.
'in' becomes 'home' ('he's in' can mean 'he's home').
'with' says to put letters next to each other.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'home'+'r'='HOMER'
(Other definitions for homer that I've seen before include "Bart Simpson's father" , "Great Greek who wrote The Iliad" , "Greek poet - TV's Simpson" , "The classical poet" , "Great Greek author of The Iliad" .)