！
Marriage? Don't make me laugh!
Literal
Marriage [subject-が] listen-[and-て] be-appalled!
聞いてあきれる is a set expression meaning 'it's absurd to even hear, don't make me laugh' — literally 'I hear it and am appalled.' The subject 結婚が is what's being heard and found ridiculous. An outburst of exasperated disbelief, likely directed at someone whose behavior contradicts the concept of marriage.