Sorry, but left the last word with board (10)
I believe the answer is:
lamentable
'sorry' is the definition.
('lamentable' can be a synonym of 'sorry')
'left the last word with board' is the wordplay.
'left' becomes 'l' (common abbreviation).
'the last word' becomes 'amen' (I've seen this before).
'with' says to put letters next to each other.
'board' becomes 'table' ('table' can be a synonym of 'board').
'l'+'amen'+'table'='LAMENTABLE'
'but' acts as a link.
(Other definitions for lamentable that I've seen before include "Deplorable, regrettable" , "Awful" , "Pitiful" , "Sorry" .)