Mr. Clennam is visiting the debtors prison:
" As they eyed the stranger in
passing, they eyed him with borrowing eyes--hungry, sharp,
speculative as to his softness if they were accredited to him, and
the likelihood of his standing something handsome. Mendicity on
commission stooped in their high shoulders, shambled in their
unsteady legs, buttoned and pinned and darned and dragged their
clothes, frayed their button-holes, leaked out of their figures in
dirty little ends of tape, and issued from their mouths in
alcoholic breathings.

The practise of begging. If it were not for the context, and the similarity to "mendicant" I would have supected it
of being a typo for "mendacity".