Board showing pasty as lacking in taste (7)
I believe the answer is:
palette
'board' is the definition.
(I know that palette is a type of board)
'pasty as lacking in taste' is the wordplay.
'pasty' becomes 'pale' (synonyms).
'lacking in' suggests deleting specific letters.
'taste' with 'as' removed is 'tte'.
'pale'+'tte'='PALETTE'
'showing' is the link.
(Other definitions for palette that I've seen before include "Board on which painter mixes colours" , "Painter's board" , "painting equipment" , "Artist's board with thumb-hole" , "Artist's colour-mixing board" .)