clobber vs beat up

clobber is a noun but beat up is not a noun.

Word	Noun	Adjective	Verb	Adverb
clobber	Yes	No	Yes	No
beat up	No	No	Yes	No

As verbs, beat up is a hypernym of clobber; that is, beat up is a word with a broader meaning than clobber:

clobber: strike violently and repeatedly
beat up: give a beating to; subject to a beating, either as a punishment or as an act of aggression

Other hypernyms of clobber include beat, work over.

clobber (noun)	beat up (noun)
informal terms for personal possessions

clobber (verb)	beat up (verb)
beat thoroughly and conclusively in a competition or fight	gather
strike violently and repeatedly	give a beating to; subject to a beating, either as a punishment or as an act of aggression