Fool adds dull brownish colour to cafe walls (5)
I believe the answer is:
dunce
'fool' is the definition.
(both can mean a stupid person)
'colour to cafe walls' is the wordplay.
'colour' becomes 'dun' (dun is a kind of colour).
'walls' says to hollow out the word (remove centre letters) (the walls are the letters on each edge).
'cafe' with its centre taken out is 'ce'.
'dun'+'ce'='DUNCE'
'adds dull brownish' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for dunce that I've seen before include "Dimwit" , "Poor student" , "Dunderhead" , "Stupid person" , "Duffer" .)