In favour of invitation that's sinister (10)
I believe the answer is:
forbidding
'sinister' is the definition.
(I know that sinister can be written as forbidding)
'in favour of invitation' is the wordplay.
'in favour of' becomes 'for' (being for a particular cause).
'invitation' becomes 'bidding' (bidding is a kind of invitation).
'for'+'bidding'='FORBIDDING'
'that's' is the link.
(Other definitions for forbidding that I've seen before include "Banning" , "sinister" , "Ominous" , "Grim" .)