Get stuck into a hefty slice (5)
I believe the answer is:
'slice' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for wedge that I've seen before include "Slice", "Piece of wood thick at one end, thin at other", "Tapering piece", "Tapered insert", "A golf club; divisive idea".)