Don't go along with errant sister (6)
I believe the answer is:
resist
'don't go along' is the definition.
I can't tell whether this defines the answer.
'errant sister' is the wordplay.
'errant' is an anagram indicator (errant can mean travelling or straying).
'sister' anagrammed gives 'RESIST'.
'with' acts as a link.
Can you help me to learn more?
(Other definitions for resist that I've seen before include "Refuse to give in to" , "Put up opposition, defy" , "Fight back" , "Stand firm against" , "Stand up to, fight against" .)