Bdtyktl

Google Translate successfully translated it to English. However I still don't understand the meaning of it (Crash, beats the clock but only if it has a stack).

I thought it might be a famous saying but Google search results given me nothing useful.

I hadn't seen this expression before, but I'd translate it differently (check below for a better option), probably something like:

The clock does strike, but only when a battery is inserted.

Which seems to mean that

"It should work, but only if certain conditions are fulfilled."

But, in light of Jacinto's answer and as can be found, e.g., here, this sentence is more likely to be a whimsical reply, in which case a better translation would be:

To strike?! It is the clock that strikes, but only if it has a battery.

Google Translate made a mess of it. I agree with Stafusa’s translation (see the other answer), but I think we get the point across better if we translate it freely as::

To strike?! It is the clock that strikes, but only if it has a battery.

or

To strike?! Striking is something a clock does, but only if it has a battery.

This is no idiom that I know of, but this structure is typical of sentences that one says, at least in Portugal, to counter or dismiss an idea presented before. And you can find a rather similar sentence used precisely for that effect on the web (Stafusa, the author of the other answer, found them; see comments to his answer). Just three instances though (this, this, and this): they mention the idea of beating (also “bater”) a child or a woman, and go on to say

“Bater, bate o relógio as horas” or ‘to strike! It is Clocks that strike the time’.

The implication is you should not bater (“beat”) a child or a woman, or anyone for that matter; because only clocks should bater (“strike”). This is of course a whimsical way to make your point, as clocks striking time have nothing to do with beating someone.

Without context I cannot be sure your sentence was used to make the same point, but it too sounds like a whimsical reply to me, and it would fit in the following example, which I made up before coming across the “bater, bate o relógio as horas” (note that bater can mean both ‘to knock’ (at a door) or (of a clock) ‘to strike’ (the time):

Ana: Não sabes bater (à porta) antes de entrar. [Can't you knock before coming in; bater = ‘to knock’ here.]

Bob: Bater, bate o relógio, mas só se tiver pilha.

Of course, clocks striking the time have nothing to do with knocking at doors, and Bob’s reply is just a whimsical way of dismissing what Ana said. It’s like saying, “Bater (‘to strike’) is for clocks; I don't bater (‘knock’)”. The first word in Bob's reply, the loose infinitive bater, just recovers and focuses attention on the key idea in what Ana said, before he goes on to counter it.