Here are the possible solutions for they can be hair raising clue
Answer
Clue
Relevancy
gels
Clue
They can be hair-raising
Definition
GEL, to become like a jelly
frightwig
Clue
Hair-raising hair
gel
Clue
It can be hair-raising
Definition
to become like a jelly
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.)
