Drainage system burning unsteadily (9)

I believe the answer is:

guttering

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'burning unsteadily' is the definition.
'guttering' can be an answer for 'burning' (thesaurus). I'm not certain of the 'unsteadily' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for guttering that I've seen before include "rain collectors" , "channel system" , "grooving?" , "threatening to go out" , "Water channel; (of candle) almost going out" .)

I've seen this clue in The Daily Express.

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