A ship beset by changing tides gets helped (8)
I believe the answer is:
assisted
'helped' is the definition.
(assisting is a kind of helping)
'a ship beset by changing tides' is the wordplay.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'beset by' means one lot of letters goes inside another ('beset' could historically mean 'cover').
'changing' indicates anagramming the letters.
'tides' anagrammed gives 'isted'.
'ss' going into 'isted' is 'ssisted'.
'a'+'ssisted'='ASSISTED'
'gets' acts as a link.
(Other definitions for assisted that I've seen before include "Lent a hand" , "Helped" , "Aided" , "to small sibling involved in stormy dates" , "given help" .)