Perfect rogue on cruise (7)
I believe the answer is:
improve
'perfect' is the definition.
(thesaurus)
'rogue on cruise' is the wordplay.
'rogue' becomes 'imp'.
'on' says to put letters next to each other.
'cruise' becomes 'rove' (both can mean to travel slowly).
'imp'+'rove'='IMPROVE'
(Other definitions for improve that I've seen before include "Enhance" , "reform" , "pick up" , "Become better" , "Get or make better" .)