you need to get the competitiveness of that keyword, on my opinion it is impossible. Because those keywords have a 0% density and prominence.
what exactly are you getting it for? It's pretty broad, and covers more things than just shoes. I'd try to break it down a bit further if it's shoes you are selling. I've been after variations of "sexy shoes" for a month and a half now. No top 10s on Google yet, but #4 on Yahoo and #2 for sexy red shoes, which is #7 on MSN. Breaking down the types of shoes would be helpful too. Like for sexy shoes, I break it down into heels, stilettos, pumps, mules, boots, etc. etc.
I think it's pretty tough. Search in google for "red shoes", got 44,700,00 results, and on page 10, it's still the keywords "red shoes" and still has sponsored link there.
This keyword is high competitive. So you need a lot of backlinks (thousands) from high PR websites to get the top ranking of Google.