Seaman knocked out, as usual (5)
I believe the answer is:
habit
'seaman knocked out as usual' is the definition.
I can't judge whether this definition defines the answer.
'seaman knocked out' is the wordplay.
'seaman' becomes 'ab' (short for able seaman).
'knocked' becomes 'hit' (I've seen this in other clues).
'out' means one lot of letters goes inside another.
'ab' placed into 'hit' is 'HABIT'.
Can you help me to learn more?
(Other definitions for habit that I've seen before include "nun gets into" , "Addiction to a drug" , "Propensity" , "can cause addiction" , "Routine - clothing" .)