Wrongdoing of family might gradually become clear (4,2)
I believe the answer is:
sink in
'clear' is the definition.
The answer and definition can be both related to thinking as well as being verbs in their base form.
Maybe there's an association between them I don't understand?
'wrongdoing of family might gradually' is the wordplay.
I cannot really see how this works, but
'wrongdoing' could be 'sin' (sin is a kind of wrongdoing) and 'sin' is located in the answer.
'family' could be 'kin' (synonyms) and 'kin' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'become' is the link.
Can you help me to learn more?
(Other definitions for sink in that I've seen before include "Register" , "(Of words) become fully understood" , "(Of facts) become fully understood" , "Get through" , "Be absorbed" .)