Very plump bottom goes on this? (4)
I believe the answer is:
sofa
'this?' is the definition.
The definition suggests a singular noun which matches the answer.
'very plump bottom goes on' is the wordplay.
'very' becomes 'so' (I've seen this in other clues).
'plump bottom goes' becomes 'fa' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on' means one lot of letters go next to another.
'so'+'fa'='SOFA'
Can you help me to learn more?
(Other definitions for sofa that I've seen before include "Divan" , "Settee" , "Somewhere to sit" , "Upholstered seat for more than one person" , "Item of furniture" .)