Crossword Genius

Shoot mouth off in second-class research establishment (4)

Ross

I believe the answer is:

blab

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'shoot mouth off' is the definition.
I can't tell whether this defines the answer.

'second-class research establishment' is the wordplay.
'second-class' becomes 'b' ().
'research establishment' becomes 'lab' (laboratory).
'b'+'lab'='BLAB'

'in' acts as a link.

Can you help me to learn more?

(Other definitions for blab that I've seen before include "Tell tales" , "Tells tales" , "Reveal secrets by indiscreet talk (colloq.)" , "Spill the beans" , "Give away secrets" .)

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