Left inside, so return; nag with a used war cry (6)

I believe the answer is:

slogan

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'used war cry' is the definition.
'slogan' can be an answer for 'cry' (thesaurus). I'm not sure about the 'used war' bit.

'left inside so return nag' is the wordplay.
'left' becomes 'l' (common abbreviation).
'inside' is an insertion indicator.
'return' is a reversal indicator.
'nag' backwards is 'gan'.
'l' going inside 'so' is 'slo'.
'slo'+'gan'='SLOGAN'

'with a' acts as a link.

Can you help me to learn more?

(Other definitions for slogan that I've seen before include "Tag line" , "Motto, catchy phrase" , "'Motto, watchword (6)'" , "Battle cry - advertising phrase" , "Catchy phrase in advertisement etc" .)

I've seen this clue in the Sydney Morning Herald.

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