Halliday & Matthiessen (2014: 495):
Although a non-finite embedded clause with a preposition is generally circumstantial in meaning, and hence enhancing, there is one other type (in addition to the perfectives with to, already noted) that is elaborating; namely those with of where the relation is appositive, e.g. the job of cleaning the barracks where the job consists in cleaning the barracks. Some of these are uncertain, e.g. the advantage of shopping early, the problem with asking directions where shopping early, asking directions could be either elaborating (appositive) ‘which consists in’ or enhancing (circumstantial) ‘which results from’.