The old sailor is first to pay the penalty (4)
I believe the answer is:
abye
'to pay the penalty' is the definition.
I can't judge whether this definition defines the answer.
'the old sailor is first' is the wordplay.
'the old' becomes 'ye'.
'sailor' becomes 'ab' (abbreviation for able seaman).
'is first' means one lot of letters go next to another.
'ye' after 'ab' is 'ABYE'.
Can you help me to learn more?
(Other definitions for abye that I've seen before include "Endure old" , "No longer endure" , "cope with penalties?" .)