Here are the possible solutions for last but one clue
Answer
Clue
Relevancy
shaft
Clue
"He's a complicated man/but no one understands him/but his woman"
disciple
Clue
All but one "The Last Supper" figure
Definition
to cause to become a follower
penult
Clue
Last but one
Definition
(Latin) the last but one syllable, also PENULTIMA
penultimate
Clue
Last but one
Definition
next to the last
rockbottom
Clue
With 133, the name of the band whose members appear in the theme answers. (They disbanded in 2012 after raising millions for literacy, but they're reuniting this weekend for one last concert.)
amaterialwitness
Clue
DESIGNER: "But I'm innocent!" LIEUT: "Maybe so, but we have ___."
frenemies
Clue
Besties who also literally hate each other's guts but we're besties but we hate each other so much it hurts sometimes
Definition
FRENEMY, a person who pretends to be a friend but is actually an enemy
