Stability-creating stuff from back lab remains for a very long time (8)

I believe the answer is:

ballasts

I'm a little stuck... Click here to teach me more about this clue!

'stability-creating stuff from back' is the definition.
I can't tell whether this defines the answer.

'lab remains for a very long time' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'lab' is 'bal' which is located in the answer.
'remains' could be 'lasts' (I've seen this in another clue) and 'lasts' is found within the answer.
No letters remain.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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