Slap bottom? (10)
I believe the answer is:
foundation
This could be a double definition.
'slap' is the first definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'bottom?' is the second definition.
(thesaurus)
Can you help me to learn more?
(Other definitions for foundation that I've seen before include "cosmetic aid?" , "Establishment" , "Artificial jet of water" , "Groundwork, basis" , "Base" .)