Sending on to be used as a shield? (10)

I believe the answer is:

forwarding

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

'sending on' is the definition.
('forward' can be a synonym of 'send on')

'to be used as a shield?' is the wordplay.
I cannot quite understand how this works, but
'to' could be 'for' and 'for' is located in the answer.
'as' could be 'in' (I've seen this in other clues) and 'in' is present in the answer.
'a' is found in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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