Picture one in a mount (5)
I believe the answer is:
monet
'picture' is the definition.
Both the definition and answer are singular nouns.
Perhaps they are linked in a way I don't understand?
'one in a mount' is the wordplay.
'in' means one lot of letters goes inside another.
'a mount' becomes 'mt'.
'one' placed inside 'mt' is 'MONET'.
Can you help me to learn more?
(Other definitions for monet that I've seen before include "French artist shown in ..." , "he painted Rouen Cathedral" , "French Impressionist with famous garden" , "Claude ---, painter (waterlilies)" , "Giverny painter" .)