A river in which to find large woman (5)

I believe the answer is:
adele
'woman' is the definition.
'a river in which to find large' is the wordplay.
'river' becomes 'dee' (River Dee).
'in which' means one lot of letters goes inside another.
'to find large' becomes 'l' (I can't justify this - if you can you should believe this answer much more).
'dee' placed around 'l' is 'dele'.
'a'+'dele'='ADELE'
Can you help me to learn more?
(Other definitions for adele that I've seen before include "Female singer from London" , "girl" , "Popular female singer" , "Performer" , "Female English singer-songwriter, b. 1988" .)
