Observing it's a dumbbell? (6)
I believe the answer is:
noting
'observing' is the definition.
('note' can be a synonym of 'observe')
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for noting that I've seen before include "Paying close attention to something" , "Observing or taking down" , "Recording in writing" , "Making brief record of something" , "Making brief record as memory aid" .)