Officer who might appear tight-lipped? (6)
I believe the answer is:
purser
'officer' is the definition.
(I know that purser is a type of officer)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for purser that I've seen before include "Ship's officer attending to the welfare of passengers" , "Naval paymaster" , "Ship's officer looking after the passengers" , "office on ship" , "Ship's officer who keeps accounts and looks after passengers" .)