Growth of Brussels? (6)
I believe the answer is:
sprout
I believe this clue is a double definition.
'growth' is the first definition.
(I've seen this before)
'brussels?' is the second definition.
(I've seen this before)
'of' is the link.
(Other definitions for sprout that I've seen before include "Small cabbage from Brussels?" , "Grow during stupor" , "Grow; vegetable" , "Produce buds" , "something for Christmas dinner?" .)