Examples of eight letter nouns that start with 'B' and end with 'K' are:
libretti
8 letter words beginning with B and ending with T: * backtalk * bankrupt * basement * besought * bookrest * bouffant * braggart * breakout
undercutunionistuppercut
slippers, scissors
destatus
Sunrisesspaciousstudioussensuoussonorousscissorssleeplessstraplessshiftlessshirtlessshinglessightlesssalacious
Charisma, chickpea, Casanova, Canberra
trickier
headache. Here's one with 9 letters - heartache
"Imperils" is a word that fits these qualifications.
ballista babushka bandanna bromelia bronchia Bulgaria
Inchworm - A small hairless caterpillar