(Cantonese analogy - figurative meaning) to break a partnership; to blow up a relation.
Definitions (粵典–words.hk)
語句
歇後語：一拍兩散 a sandwich pun which the later part is "one blow disperses two"; means to break up a joint enterprise or relationship when neither party comes out a winner (sometimes used as a threat during a negotiation). Literally: a fly stalking a horse tail