Laird, perhaps, in an unhappy mood by end of tribunal (9)
I believe the answer is:
landowner
'laird perhaps' is the definition.
(laird is a kind of landowner)
'an unhappy mood by end of tribunal' is the wordplay.
'unhappy mood' becomes 'downer'.
'by' is a charade indicator (letters next to each other).
'end of' indicates one should take the final letters.
The final letter of 'tribunal' is 'l'.
'an'+'downer'='andowner'
'andowner' put after 'l' is 'LANDOWNER'.
'in' is the link.
(Other definitions for landowner that I've seen before include "One with title to an area" , "Man of means" , "One may have lots of grass" , "One possessing estate" , "Squire, perhaps" .)