Duck, Sir Francis! (5)
I believe the answer is:
drake
I believe this is a double definition.
'duck' is the first definition.
(drake is a male duck)
'sir francis' is the second definition.
(I've seen this in another clue)
(Other definitions for drake that I've seen before include "Plymouth bowler" , "English circumnavigator, d. 1596" , "-'s Drum (Newbolt)" , "Elizabethan sailor" , "old sailor" .)