翻译和我的解释

I could not find the direct reference to the phrase "drop the groves'.  But from the way that people use it the meaning of the phrase is clear to me.  It means the ice hockey players (are ready to )fight physically.  So the translation will be “我们不会先动手， 但是如果你们（对方）动手打人我们也不会客气（会还击）”。  The use of this phrase is limited in the conversation about the ice hockey games, which is very physical and involves a lot of physical fights.

I tried to guess the origination of the phrase.  "grove" is connected to small place where the tree grows.  It may in turn refer to cluster of few trees and then refers to a cluster of wood posts of sticks.  The ice hockey players have sticks in there hands when they play normally.  But when they quarrel and fight physically they drop the sticks and use fists and legs( using sticks to hit the opponents is still possible though, but it goes to extremes.).

It is just a guess.  Hope that somebody gives better explanation.