Foolish mother supported by daughter (3)
I believe the answer is:
mad
'foolish' is the definition.
('mad' can be similar in meaning to 'foolish')
'mother supported by daughter' is the wordplay.
'mother' becomes 'ma' (ma is a kind of mother).
'supported by' says to put letters next to each other (letters go below - in down clue).
'daughter' becomes 'd'.
'ma'+'d'='MAD'
(Other definitions for mad that I've seen before include "Crazed" , "Frenzied" , "Roused to anger" , "Crackers" , "Angry or insane" .)