The most common and most likely answer to this crossword clue is the 10 letter word STEPMOTHER
I've seen this crossword clue in The Guardian
S
T
E
P
M
O
T
H
E
R
More clues leading to the result STEPMOTHER
- Copper comes in to arrest different relative
- Sulks about test woman gives relative
- Member of family to stifle upset favourite being protected
- Son gets awfully hot temper from family member …
- Second mate who raises the issue?
- What man’s partner may be? Protest he must be upset about origin of money
- Unoriginal kin with awful hot tempers
- Hot tempers disturbed a parental figure
Buddy explains!

The straight part
We know that "Member of family" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case member of family = stepmother.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does STEPMOTHER mean?
STEPMOTHER noun- The wife of one's biological father, other than one's biological mother.
- A viola, especially Viola tricolor, heartsease.