Crossword Genius

Service chief backs small member of big organisation (3)

Ross

I believe the answer is:

cog

I'm a little stuck... Click here to teach me more about this clue!

This clue might be a double definition.

'service chief backs small' is the first definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I can't see?

'member of big organisation' is the second definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

Can you help me to learn more?

(Other definitions for cog that I've seen before include "Machine component" , "One on a gearwheel" , "Projection on a toothed wheel" , "one engaged in revolutionary activity" , "Minor player" .)

I've seen this clue in The Daily Mail.
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