They're mostly forward (5)

I believe the answer is:

gears

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

'forward' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for gears that I've seen before include "Sarge (anag.)" , "Rages (anag.)" .)

I've seen this clue in the Evening Standard.

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