Physicist inventing tube is daring — no good missing out (7)
I believe the answer is:
venturi
'physicist inventing tube' is the definition.
(Giovanni Venturi, inventor of the Venturi tube)
I can't explain the remainder of the clue.
(Other definitions for venturi that I've seen before include "flow measure" , "Narrow section of tube for measuring flow rate" , "Tube to regulate flow" , "Narrow tube for measuring flow rates" , "tube used to control fluid flow" .)