Being one of the family, is naturally upset at first (4)
I believe the answer is:
aunt
But I can't explain it at all! Could you help me understand?
(Other definitions for aunt that I've seen before include "Charley's in play?" , "Charley's ___ , farce staged in London in 1892, revived and adapted ever since" , "Family relative" , "Female relation" , "Parent's female sibling" .)