Pirate ship's original bearing, by crikey! (7)
I believe the answer is:
corsair
'pirate' is the definition.
(I know that Corsair is a type of pirate)
'ship's original bearing by crikey' is the wordplay.
'original' says to take the initial letters (the origin of the word).
'bearing' becomes 'air' (both can mean an attitude or pose).
'by' means one lot of letters go next to another.
'crikey' becomes 'cor' (both are expressions of surprise).
The first letter of 'ships' is 's'.
's'+'air'='sair'
'sair' put after 'cor' is 'CORSAIR'.
(Other definitions for corsair that I've seen before include "Marauder" , "Pirate (archaic)" , "Seafarer" , "20 across" , "Pirate from N. Africa" .)