Neither did I - until I looked up "footprint" in my Bradford's Crossword Solver's Dictionary (an invaluable resource)
[I hope you read this earthakitten!]
Hi crofter ... I used Bradfords at the weekend to get that one, saw the question from GC and thought, 'I know that one' to find you had already answered. Must be a little quicker next time kitten !! Have I told you yet that I am in love with Bradfords ! xx