Simply remove a url segment with .htaccess
Assuming no further rewrites are in use, and all links inside /entry/
are to rewritten, then try this:
RewriteEngine on
RewriteBase /
RewriteRule ^/entry/(.+)$ /$1 [L,QSA]
Lose the [L]
if there are further rewrites ahead in the file.
Although this has already been answered, it didn't work for me when I had two segments after the first, eg:
http://foo.com/entry/random-segment/random-entry-123
Instead this worked for me and also takes care of 301 redirects:
RedirectMatch 301 /entry/(.*) /$1
Hope this helps.