In trouble, guards the family members (9)
I believe the answer is:
daughters
'family members' is the definition.
(daughter is a type of relative)
'in trouble guards the' is the wordplay.
'in trouble' indicates anagramming the letters.
'guards'+'the'='guardsthe'
'guardsthe' is an anagram of 'DAUGHTERS'.
(Other definitions for daughters that I've seen before include "The guards turn out to be relatives" , "Female offspring" .)