How do I check man pages for what single parameter of the command does?

Search

x is for extract.

After you are inside man, type /-xenter to search info about the -x parameter,
Press n to jump to the next -x match, and N for the previous

Search with Regex

For large man pages, or a common terms, a little regex can be used to narrow the search.

If you just want the main entry, you can use /^ *-x to remove most extraneous matches.
This works as most man pages are formatted with the entry indented with spaces.

• ^ * matches the start of line, with zero to many spaces.
• -x is the search string.

This works in RHEL6 with Bash

In .bashrc

add

function mans {
       man $1 | less -p "^ +$2"
}

start a new instance of bash

$ bash

now

mans ls -l

has the desired effect.

You could also grep it out of the man page with some context:

man tar | grep -C5 -- '-x\b'