Defenders drinking and congratulating each other (12)

I believe the answer is:

backslapping

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

'congratulating each other' is the definition.
I can't tell whether this definition defines the answer.

'defenders drinking' is the wordplay.
'defenders' becomes 'backs' (I've seen this before).
'drinking' becomes 'lapping' (lapping is a kind of drinking).
'backs'+'lapping'='BACKSLAPPING'

'and' acts as a link.

Can you help me to learn more?

(Other definitions for backslapping that I've seen before include "Hearty" , "Demonstratively cheery" .)

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

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