The most common and most likely answer to this crossword clue is the 5 letter word VALVE
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More clues leading to the result VALVE
- Regulator very vigorous? Not I
- So long screening very old television part
- Last word said about very on-off device
- Gents perhaps put up five to lead energy regulator
- Regulator of volume brought in to see what’s in a pint?
- Toilet turned over, stripped to find ballcock
- Mollusc shell in device used for flow control
Buddy explains!

The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does VALVE mean?
VALVE noun- A device that controls the flow of a gas or fluid through a pipe.
- A device that admits fuel and air into the cylinder of an internal combustion engine, or one that allows combustion gases to exit.
- One or more membranous partitions, flaps, or folds, which permit the passage of the contents of a vessel or cavity in one direction, but stop or control the flow in the opposite direction
- One of the leaves of a folding-door, or a window-sash.
- A vacuum tube.
- One of the pieces into which certain fruits naturally separate when they dehisce.
- A small portion of certain anthers, which opens like a trapdoor to allow the pollen to escape, such as in the barberry.
- One of the pieces or divisions of bivalve or multivalve shells.
- One of the two similar portions of the shell of a diatom.
- To control (flow) by means of a valve.