Terrible boredom without party game (5)
I believe the answer is:
ombre
'game' is the definition.
(thesaurus)
'terrible boredom without party' is the wordplay.
'terrible' indicates anagramming the letters.
'without' is a deletion indicator.
'party' becomes 'do' (do is a kind of party).
'boredom' with 'do' taken out is 'borem'.
'borem' with letters rearranged gives 'OMBRE'.
(Other definitions for ombre that I've seen before include "Three-player card game" , "Tricky game" , "Card-game for three; rob me (anag.)" , "With blending colours" , "Shaded" .)