Flesh out support provided by board (5)
I believe the answer is:
shelf
'board' is the definition.
(I've seen this before)
'flesh out support provided' is the wordplay.
'flesh' can be anagrammed to 'SHELF'.
Though, I'm not clear how the anagram is indicated.
'by' is the link.
Can you help me to learn more?
(Other definitions for shelf that I've seen before include "Whereon 2 down is not!" , "A place to store" , "books supporter" , "Sill" , "Projecting ridge on a mountain" .)