Cycling mayor's on board to make cuts (6)
I believe the answer is:
'cuts' is the definition.
(shank is a kind of cut)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for shanks that I've seen before include "Cuts of meat from the upper part of the leg" , "Walk - go by . . . . . . Mare" .)