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