A send-up on board produces melancholy (7)
I believe the answer is:
sadness
'melancholy' is the definition.
(I've seen this before)
'a send-up on board' is the wordplay.
'up' indicates anagramming the letters (letters get chucked up).
'on board' becomes 'ss' (I've seen this in other clues).
'a'+'send'='asend'
'asend' with letters rearranged gives 'sadne'.
'sadne'+'ss'='SADNESS'
'produces' acts as a link.
(Other definitions for sadness that I've seen before include "Gloom" , "Misery" , "blues" , "Depression" , "Dolour" .)