Let it be Penny's decision (4,1,4)

I believe the answer is:

toss a coin

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'decision' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'let it be penny's' is the wordplay.
'let' becomes 'tos' (I am not sure about this - if you are sure you should believe this answer much more).
'it' becomes 'sa' (old-fashioned abbreviation for sex appeal).
'be penny' becomes 'coin' (I've seen this in another clue).
'tos'+'sa'+'coin'='TOSS A COIN'

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I've seen this clue in the Evening Standard.

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