Sometimes in order to achieve something or complete a task, you resort to any method available to you. You are not too worried about whether what you are doing is ethical or not; you are intent on achieving your goal. As a result, you end up doing things in an unplanned and an unsystematic manner. This is what `catch as catch can’ means. The idiom has more or less the same meaning as `no holds barred’.
*When his former partner complained that he was taking away his clients, Rahul told him that in business it was a case of catch as catch can.
Are you a fan of WWF wrestling? If you are, then you will understand what the word `catch’ refers to. In freestyle wrestling, there are no restrictions on how you can hold your opponent. You can `catch’ or hold him/her in any way you can.