excuse vs fend for

excuse is a noun but fend for is not a noun.

Word	Noun	Adjective	Verb	Adverb
excuse	Yes	No	Yes	No
fend for	No	No	Yes	No

As verbs, fend for is a hypernym of excuse; that is, fend for is a word with a broader meaning than excuse:

Other hypernyms of excuse include defend, support.

excuse (noun)	fend for (noun)
a poor example
a defense of some offensive behavior or some failure to keep a promise etc.
a note explaining an absence

excuse (verb)	fend for (verb)
accept an excuse for	argue or speak in defense of
defend, explain, clear away, or make excuses for by reasoning
excuse, overlook, or make allowances for; be lenient with
serve as a reason or cause or justification of
grant exemption or release to
ask for permission to be released from an engagement