Flat bottom on which daughter stands (5)
I believe the answer is:
drear
'flat bottom on which daughter stands' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I don't see?
'flat bottom on' is the wordplay.
'flat' becomes 'd' (I can't justify this - if you can you should give a lot more credence to this answer).
'bottom' becomes 'rear' (synonyms).
'on' means one lot of letters go next to another.
'd'+'rear'='DREAR'
Can you help me to learn more?
(Other definitions for drear that I've seen before include "gloomy in poem" , "Grim" , "Dismal (literary)" , "Depressingly dull" , "Dismal, dull" .)