One villain after power in a boat (7)
I believe the answer is:
pirogue
'a boat' is the definition.
(thesaurus)
'one villain after power' is the wordplay.
'one' becomes 'i' (Roman numeral).
'villain' becomes 'rogue' (rogue is a kind of villain**).
'after' is a charade indicator (letters next to each other).
'power' becomes 'p'.
'i'+'rogue'='irogue'
'irogue' put after 'p' is 'PIROGUE'.
'in' acts as a link.
(Other definitions for pirogue that I've seen before include "shallow conveyance" , "hollow craft" , "Dugout canoe" , "One needing a row" .)