Why would the term "tank top" be too girly? That's exactly what I would call a man's shirt like that ... there isn't a different term, as far as I know.
There are (thin, white) tank top undershirts, but I can't see Clark wearing one and especially not to bed. Jonathan, maybe. It has an "older man" connotation to me ... something my dad would wear but not my husband. (Though my husband does wear regular white t-shirt undershirts under business clothing.)
When Clark sleeps on the show, he either wears boxer shorts or sleep shorts alone, or he pairs the sleep shorts with a regular t-shirt or muscle shirt (t-shirt with the sleeves cut off). I don't know that we've ever seen him in a real tank top ... not that I can recall, in any case. Even that episode where he took Jonathan to the health club, I think he was wearing a muscle shirt -- it seems to be his choice for lounging clothes.
Kathy
