würde ich vorschlagen, bin allerdings kein Muttersprachler

i.e. not fancy, loud, gaudy...

"Simple" would work, but since this is about typography you might want to consider something more specific. Grotesques are technically a subset of sans-serifs but could be used as a synonym here.

serifs (more generally known as grotesques or antiques) and slab-serifs ...
keithtam.net/documents/slabserif.pdf

(Univers and Helvetica are both grotesques. ...
www.typography.com/catalog/gotham/features.html

The first sans serifs, sometimes referred to as grotesques or Gothics, were relatively monotone in character. They first appeared in an 1816 specimen book ...
http://www.historychannel.com/thcsearch/thc_resourcedetail.d...


Just another suggestion...



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Note added at 1 hr (2006-07-19 00:12:54 GMT)
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That first reference is actually bit misleading, so here's another one:

The grotesques where so named because the public were initially somewhat shocked by their relatively stark design. Grotesques are very bare in appearance due to the absence of serifs, and the simpler, cleaner designs. Because of their ``in your face'' appearance, grotesques are good for headlines.
pegasus.rutgers.edu/~elflord/font_howto/Font-HOWTO/html/Font-HOWTO/x87.html

File Format: PDF/Adobe Acrobat - View as HTML
Select an unembellished font such as Arial,. •. Avoid italics, bold and underlining,. •. Use keywords to identify skills and abilities the employer is ...
www.maryville.edu/academics/ careeredu/PDF/Resumes_%20Portfolios.pdf - Similar pages


TYPO-L Archives -- May 2000 (#600)fonts of all orientations beckoning, why not use a simple unembellished font for, say, running heads? OK, one can make a case for using that combination ...
https://listserv.heanet.ie/cgi-bin/ wa?A2=ind0005&L=typo-l&T=0&P=62566 - 14k -

or instead of "clean/with clean lines" you could say "unfussy"