Lying around is Romeo's captive (8)
I believe the answer is:
prisoner
'captive' is the definition.
(synonyms)
'lying around is romeo's' is the wordplay.
'lying' becomes 'prone' (I've seen this before).
'around' indicates putting letters inside.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'prone' enclosing 'is' is 'prisone'.
'prisone'+'r'='PRISONER'
(Other definitions for prisoner that I've seen before include "Condemned" , "One is incarcerated" , "One locked up" , "Rep irons out the captive" , "Captive or criminal in jail" .)