A ferry scuttled to become lighter (6)
I believe the answer is:
rarefy
'become lighter' is the definition.
The answer and definition can be both related to change as well as being verbs in their base form.
Perhaps there's a link between them I don't understand?
'a ferry scuttled' is the wordplay.
'a ferry' anagrams to 'RAREFY'.
But, I'm not sure how this is indicated.
'to' is the link.
Can you help me to learn more?
(Other definitions for rarefy that I've seen before include "Become less dense" , "To make less dense" , "Make less solid; a ferry (anag.)" , "Thin" , "Make thinner" .)