Drop key objective following board's conclusion (7)
I believe the answer is:
descend
'drop' is the definition.
(thesaurus)
'key objective following board's conclusion' is the wordplay.
'key' becomes 'esc' ('Escape' key on a computer keyboard).
'objective' becomes 'end' (I've seen this before).
'following' says to put letters next to each other.
'conclusion' indicates one should take the final letters.
The last letter of 'board' is 'd'.
'esc'+'end'='escend'
'escend' after 'd' is 'DESCEND'.
(Other definitions for descend that I've seen before include "Alight" , "Come down" , "Climb down" , "Move downward" , "Sink" .)