Moves a certain distance in a ship (5)
I believe the answer is:
sways
'moves' is the definition.
The definition and answer can be both acts as well as being plural nouns.
Perhaps there's a link between them I don't understand?
'a certain distance in a ship' is the wordplay.
'a certain distance' becomes 'way' (way is a kind of distance. I am not sure about the 'certain' bit.).
'in' means one lot of letters goes inside another.
'a ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'way' inserted inside 'ss' is 'SWAYS'.
Can you help me to learn more?
(Another definition for sways that I've seen is " Swings".)