In earnest, one snatched weights (6)
I believe the answer is:
stones
'weights' is the definition.
(stone is a kind of weight)
'in earnest one snatched' is the wordplay.
'in' says the answer is hidden in the clue.
'STONES' is hidden within 'earnest one snatched'.
(Other definitions for stones that I've seen before include "Attacks" , "Rolling ones gather no moss, it's said" , "Weights and pieces of rock." , "Cherry pips" , "Gems -- Mick Jagger's rollers?" .)