Gerunds function as subjects, objects of the verb, ad objects of prepositions. In our example sentence, below, 'of' is a preposition which makes 'stealing food' its object, a gerund.
 A friend of mine was accused of stealing food.
Another way to tell if it's a gerund, a noun, and not a verb, is to replace the -ing word with a pronoun,
A friend of mine was accused of this.
Looking now at your second example, , what role does 'cutting' play? Is it the object of the verb 'wants'? Yes.
 The grass wants cutting this week.
Note, in that context 'wants' is synonymous with needs,
The grass needs cutting. (Gerund)
The grass needs to be cut. (to-infinitive)
Max needs a hair cut. (noun phrase)
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