And not the last sightings of Captain Horatio Hornblower (3)
I believe the answer is:
nor
'and not' is the definition.
('nor' means 'and also not')
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for nor that I've seen before include "In addition, not" , "Negative word" , "And not either" , "Neither one ... the other" , "It's also not" .)