Various letters providing support for the board (7)
I believe the answer is:
trestle
'support for the board' is the definition.
(cryptic definition)
'various letters' is the wordplay.
'various' is an anagram indicator.
'letters' with letters rearranged gives 'TRESTLE'.
'providing' acts as a link.
(Other definitions for trestle that I've seen before include "Letters about a table support" , "Framework to support a flat surface -- letters (anag)" , "Support for table top" , "Simple table support" , "Framework for holding a tabletop" .)