Daughter is, y'know, showing hostility (7)
I believe the answer is:
dislike
'hostility' is the definition.
(I've seen this before)
'daughter is y'know' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'y'know' becomes 'like' (I am not sure about this - if you are sure you should believe this answer much more).
'd'+'is'+'like'='DISLIKE'
'showing' is the link.
Can you help me to learn more?
(Other definitions for dislike that I've seen before include "Fell aversion or antipathy" , "Hate" , "Feel distaste for (something)" , "Loathe" , "Can't stand" .)