I just figured out how to do this:

$ zhelp() { man zshbuiltins | less -p "^       $1" }

$ zhelp read

      read [ -rszpqAclneE ] [ -t [ num ] ] [ -k [ num ] ] [ -d delim ]
             [ -u n ] [ name[?prompt] ] [ name ...  ]
      ....

... simple and effective, but I'll bet someone has something better.