Reading into departure, being a pig? (7)

I believe the answer is:

gorging

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'being a pig?' is the definition.
Although both the answer and definition are present participle verbs, I cannot see how they can define each other.

'reading into departure' is the wordplay.
'reading' becomes 'rg' (I can't explain this - if you can you should believe this answer much more).
'into' indicates putting letters inside.
'departure' becomes 'going' (synonyms).
'rg' inserted within 'going' is 'GORGING'.

Can you help me to learn more?

I've seen this clue in The Daily Express.

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