Complete Charlie must leave sailing ship (5)
I believe the answer is:
utter
'complete' is the definition.
(I know that complete can be written as utter)
'charlie must leave sailing ship' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'must leave' suggests deleting specific letters.
'sailing ship' becomes 'cutter' (cutter is a kind of sailing ship).
'cutter' with 'c' taken away is 'UTTER'.
(Other definitions for utter that I've seen before include "Express audibly" , "in toto" , "Say - complete" , "Absolute - say" , "Complete; absolute" .)