Crossword puzzle clue "this puzzle's nine longest answers use only the first half of it"

a set of letters

a space, esp. an enclosed one, around a building (e.g. a cathedral, college, etc.)

to live in a lair

to try to catch cold-blooded aquatic vertebrates

to shoot with a gun (a portable firearm)

to move by jumping on one foot

LINE, to mark out with slender, continuous marks