kěn
to gnaw
to nibble; to bite
The mouth radical (口) drives the meaning here — gnawing is an action of the mouth, often slow and deliberate. 肯 contributes the sound kěn and carries no semantic load in this character.
狗在啃一根骨头。
gǒu zài kěn yī gēn gǔ tou。
The dog is gnawing on a bone.
她慢慢地啃着玉米,吃得很开心。
tā màn màn de kěn zhe yù mǐ,chī de hěn kāi xīn。
She nibbled on the corn slowly, eating very happily.
啃书
kěn shū
lit. to gnaw a book
啃老
kěn lǎo
(coll.) to live with and depend on one's parents even upon reaching adulthood
啃老族
kěn lǎo zú
(coll.) adults still living with and depending on their parents
嘴啃泥
zuǐ kěn ní
to fall flat on one's face