Spots a flapper when undecided (9)

I believe the answer is:

seesawing

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'when undecided' is the definition.
I can't judge whether this defines the answer.

'spots a flapper' is the wordplay.
'spots' becomes 'sees' (I've seen this in another clue).
'a flapper' becomes 'awing' (I am not sure about this - if you are sure you should believe this answer much more).
'sees'+'awing'='SEESAWING'

Can you help me to learn more?

(Other definitions for seesawing that I've seen before include "going up and down" , "may show fluctuation" , "Swinging" .)

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

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