Left switch to chance (3)
I believe the answer is:
lot
'chance' is the definition.
(as in drawing by lot)
'left switch to' is the wordplay.
'left' becomes 'l' (common abbreviation).
'switch' says the letters should be written backwards (I've seen 'switched' mean this).
'to' reversed gives 'ot'.
'l'+'ot'='LOT'
(Other definitions for lot that I've seen before include "Large amount; Abraham's nephew" , "Destiny - auction item(s)" , "Survivor in Sodom" , "Can be many or one auction item" , "Fortune" .)