A French friend in front of a board is disagreeable (11)
I believe the answer is:
unpalatable
'disagreeable' is the definition.
(similar in meaning)
'a french friend in front of a board' is the wordplay.
'a french' becomes 'un' ('a' in French).
'friend' becomes 'pal' (pal can mean a friend).
'in front of' means one lot of letters go next to another.
'board' becomes 'table' (both can mean food).
'un'+'pal'+'a'+'table'='UNPALATABLE'
'is' is the link.
(Other definitions for unpalatable that I've seen before include "not tasty" , "Not pleasant to taste" .)