reason vs fend for

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

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

As verbs, fend for is a hyponym of reason; that is, fend for is a word with a more specific, narrower meaning than reason:

Other hyponyms of reason include re-argue, expostulate, defend, support.

reason (noun)	fend for (noun)
the capacity for rational thought or inference or discrimination
a fact that logically justifies some premise or conclusion
a justification for something existing or happening
an explanation of the cause of some phenomenon
a rational motive for a belief or action
the state of having good sense and sound judgment

reason (verb)	fend for (verb)
think logically	argue or speak in defense of
decide by reasoning; draw or come to a conclusion
present reasons and arguments