Depend on us returning, surely (4)

I believe the answer is:

rely

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

'depend' is the definition.
(I know that depend can be written as rely)

'us returning surely' is the wordplay.
'RELY' is hidden within the letters.
However, I am uncertain how this is indicated.

'on' acts as a link.

Can you help me to learn more?

(Other definitions for rely that I've seen before include "Depend or lean on" , "Depend (upon)" , "Old rally" , "Trust, depend" , "All the letters" .)

I've seen this clue in the Evening Standard.

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