Okay, as far as I can tell there doesn't seem to be anything clearly defining what counts as Clothing, Armor, or both, other than common sense... which seems to not be enough to keep there from being some massive headaches (see my thread about PPP for an example:
http://forums.shadowrun4.com/index.php?topic=5340.0). Specific page reference would be the section on "Clothing and Armor" in SR4A, p326.
There apparently needs to be a more explicit statement of the relationships between what is considered "clothing", what is considered "armor" and what, if anything, is considered both.
This is further complicated by the entry for the SecureTech PPP-System gear (Arsenal, p49) which states
"Each piece of armor is available in at least three styles: as discreet protection designed to be worn beneath other clothing, as an obvious strapped addition to other visible armor, and as sports equipment."As the aforementioned thread has proven, there's quite a bit of room for dispute about the definition of "visible armor", as well as whether the "discreet protection" version can be worn beneath items listed in the Armor table in the Core book, such as Armor Clothing or the Urban Explorer Jumpsuit (SR4A, p326 again), as well as the "Armor Clothing" fashion items from Arsenal (p44-48).
While it seems perfectly obvious to me that "visible armor" is defined as "armor that
looks like armor" and "yes", respectively, the aforementioned thread rather proves that either the word "visible" should either be changed to "obvious", or some further clarification that armor is not clothing, and which things count as what, needs to be added.
If my interpretation is the correct one, it might actually cause less literal-interpretation-of-RAW-vs-logic headbutting if the entry is rewritten to say something like
"Each piece of armor is available in at least three styles: as discreet protection that can be worn beneath other layers, obvious strapped pads that are worn worn on top, and as sports equipment." Note the removal of all references to to 'armor' or 'clothing' while maintaining essentially the same information.