First to board ship after a son helps (7)
I believe the answer is:
assists
'helps' is the definition.
(assisting is a kind of helping)
'first to board ship after a son' is the wordplay.
'first to' becomes 'ist' (I've seen this in other clues).
'board' means one lot of letters goes inside another.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'after' is a charade indicator (letters next to each other).
'son' becomes 's' (genealogical abbreviation for son).
'ist' inserted inside 'ss' is 'sists'.
'a'+'s'='as'
'sists' put after 'as' is 'ASSISTS'.
(Other definitions for assists that I've seen before include "Contributes to success" , "Aids" , "Helps or waits on" , "Lends a hand" , "Provides" .)