Seeing that side is rocking (6)

I believe the answer is:

aswing

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'rocking' is the definition.
Both the definition and answer are present participle verbs.
Maybe they are linked in a way I don't understand?

'seeing that side' is the wordplay.
'seeing that' becomes 'as' (I've seen this in other clues).
'side' becomes 'wing' (I've seen this in other clues).
'as'+'wing'='ASWING'

'is' acts as a link.

Can you help me to learn more?

I've seen this clue in The Times.

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