Honey, obviously it can not be tight, see-through nor short.. That is out of the question. But you can wear anything you wish as long as it isn't immatating men and it is loose. Go for it. Cabaayad and Salwar's recommended but skirts are cool too. {I sometimes wonder if my salwar is like men's kameez?!Hmm, its depressing-My father says no, but anyhow..}
I remember seeing this girl all the time when I first moved to my area-She was always fully covered (Very long Skirt someone swiping the floor, Hijab) until you passed her ..

OMG she had the biggest ass ever, actually it probley wasnt all that but its because shes wearing a short top and definatly the wrong material skirt which clinged to her arse. Now how is that for modest?She may of just went out without it. It was shooking walahi. So some skirts aren't so cool after all
