Oppose the freeing of one's sister? (6)
I believe the answer is:
resist
'oppose' is the definition.
(resisting is a kind of opposing)
'freeing of one's sister?' is the wordplay.
'sister' anagrams to 'RESIST'.
Though, I'm not sure how the anagram is indicated.
'the' acts as a link.
Can you help me to learn more?
(Other definitions for resist that I've seen before include "Oppose, put up defence" , "Use force to prevent something from happening to sister" , "Express opposition" , "Don't give in" , "Withstand, oppose" .)