Hi,
- org-clock-into-drawer is customized to "PROPERTIES"
- so both CLOCK and Effort properties should go in the PROPERTIES drawer- it works in Org-mode version 8.2.10 (release_8.2.10 @ d:/bin/emacs-24.5/share/emacs/24.5/lisp/org/)  - result:    :PROPERTIES:
    CLOCK: [2016-02-22 Mon 15:26]    :Effort:   1w    :END:- it does *not* work in Org-mode version 8.3.3 (8.3.3-55-g9f7d7b-elpa @ d:/ddc/.emacs.d/elpa/org-20160215/)
  - result:    :PROPERTIES:
    :Effort:   1w    :END:    :PROPERTIES:    CLOCK: [2016-02-22 Mon 15:26]    :END:
David