gistfile1.rb

# in the engine
ActionController::Routing::Routes.draw do |map|
  map.resources :users, :controller => 'clearance/users' do |users|
    users.resource :password,
      :controller => 'clearance/passwords',
      :only => [:create, :edit, :update]
end

# in the app
ActionController::Routing::Routes.draw do |map|
  map.resources :users
end