seize vs clench

seize is not a noun while clench is a noun.

Word	Noun	Adjective	Verb	Adverb
seize	No	No	Yes	No
clench	Yes	No	Yes	No

As verbs, clench is a hyponym of seize; that is, clench is a word with a more specific, narrower meaning than seize:

seize (noun)	clench (noun)
	the act of grasping
	a small slip noose made with seizing

seize (verb)	clench (verb)
capture the attention or imagination of	hold in a tight grasp
affect	squeeze together tightly
take into your hands deliberately
take or capture by force
hook by a pull on the line
take possession of by force, as after an invasion
take temporary possession of as a security, by legal authority
seize and take control without authority and possibly with force; take as one's right or possession