I tend to agree, parallelogram. For the clue to work , either 1) "advantage" must be synonymous with "a", or 2) "initially" must do double duty to indicate both the first letter and where it must appear in the answer, or 3) "with" must be used in the sense that "a with b" could mean either "ab" or "ba". I don't know which is intended, possibly the last, but none seems ideal