Crude picture of fish swallowing half of us (4)
I believe the answer is:
daub
'crude picture' is the definition.
'daub' can be an answer for 'picture' (daub is a kind of picture). I'm not sure about the 'crude' bit.
'fish swallowing half of us' is the wordplay.
'fish' becomes 'dab' (dab is a type of fish).
'swallowing' indicates putting letters inside.
'half of' indicates taking half.
'us' cut in half is 'u'.
'dab' going around 'u' is 'DAUB'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for daub that I've seen before include "Amateurish painting" , "Plaster; paint crudely" , "Smear roughly or paint clumsily" , "Smear; plaster" , "Smear; bad painting" .)