Humble dwelling covered by river (7)
I believe the answer is:
deflate
'humble' is the definition.
(thesaurus)
'dwelling covered by river' is the wordplay.
'dwelling' becomes 'flat' (I can't justify this - if you can you should give a lot more credence to this answer).
'covered by' is an insertion indicator.
'river' becomes 'dee' (River Dee).
'flat' going into 'dee' is 'DEFLATE'.
Can you help me to learn more?
(Other definitions for deflate that I've seen before include "Let air out of, like balloon" , "Puncture, collapse like balloon" , "Let the wind out of, braggart or balloon" , "Cause to shrink or collapse" , "Release air from" .)