Fall over the pond, as the British say, before winter (6)
I believe the answer is:
autumn
'winter' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for autumn that I've seen before include "part of year?" , "Fall for 33 across" , "When harvests ripen" , "1 Season of mists and mellow fruitfulness" , "Fall in the US" .)