anchor vs drop anchor

anchor is a noun but drop anchor is not a noun.

Word	Noun	Adjective	Verb	Adverb
anchor	Yes	No	Yes	No
drop anchor	No	No	Yes	No

As verbs, anchor and drop anchor are synonyms defined as:

Other synonyms of anchor include cast anchor.

anchor (noun)	drop anchor (noun)
a mechanical device that prevents a vessel from moving
a central cohesive source of support and stability
a television reporter who coordinates a broadcast to which several correspondents contribute

anchor (verb)	drop anchor (verb)
secure a vessel with an anchor	secure a vessel with an anchor
fix firmly and stably