Tribunal, primarily, needs to be given motive for crime (7)
I believe the answer is:
treason
'for crime' is the definition.
(treason is a kind of crime)
'tribunal primarily needs to be given motive' is the wordplay.
I cannot quite see how this works, but
'motive' could be 'reason' (reason is a kind of motive) and 'reason' is present in the answer.
A single letter 't' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for treason that I've seen before include "Stare on (anag.)" , "Betrayal of the state" , "Mutiny" , "One's art? (anag)" , "Perfidy" .)