Lots of heavy weights (4)
I believe the answer is:
tons
I believe this clue is a double definition.
'lots of' is the first definition.
(I've seen this in another clue)
'heavy weights' is the second definition.
(I've seen this in another clue)
(Other definitions for tons that I've seen before include "Each is equivalent to 2240 pounds" , "Lots" , "A lot" , "Loads (sl.)" .)