Misguided letters in support of the board (7)
I believe the answer is:
trestle
'support of the board' is the definition.
'trestle' can be an answer for 'support' (I've seen this before). I'm not certain of the 'of the board' bit.
'misguided letters' is the wordplay.
'misguided' indicates anagramming the letters (letters guided into the wrong places).
'letters' anagrammed gives 'TRESTLE'.
'in' is the link.
Can you help me to learn more?
(Other definitions for trestle that I've seen before include "support of growth" , "Simple table support" , "Frame supporting table" , "Table support frame" , "Frame to hold table" .)