Turning valves produced liquid (4)

I believe the answer is:

spat

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'liquid' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for spat that I've seen before include "Row; discharged" , "Small altercations between Pats" , "Legging covering instep and ankles" , "Petty quarrel or fight" , "Gestured with contempt" .)

I've seen this clue in The Times.

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