Hi Dutchy,
Your answer 'grossly' is correct!
104D. Hugely- Grossly
My Oxford Dictionary Of English definition of 'gross' in the sense that the clue is seeking is:
Gross- 5. General or large-scale.
My Reader's Digest Word Power Dictionary definition of 'gross' in the sense that the clue is seeking is:
Gross > adjective 1. Unattractively large or bloated.
And the clincher....
My Reader's Digest Special Deluxe Edition Chambers Crossword Dictionary:
synonyms for 'gross'
4 Letters- huge
5 Letters- large
Hope this helps!
Talk to you again soon Dutchy.
Warm regards, Butterfly