Daughter and wife allowed a drop (7)
I believe the answer is:
driblet
'a drop' is the definition.
(I know that drop can be written as driblet)
'daughter and wife allowed' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'and' means one lot of letters go next to another.
'wife' becomes 'rib'.
'allowed' becomes 'let' (to let is to allow or permit).
'd'+'rib'+'let'='DRIBLET'
(Other definitions for driblet that I've seen before include "tiny stream" , "tiny bit" , "a little water" , "Very small quantity of a liquid" , "small amount" .)