Survey questions linked to small mail shot for those in their sixties? (11)

I believe the answer is:

sexagesimal

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'survey questions' is the definition.
The definition suggests a singular noun which matches the answer.

'linked to small mail shot for those in their sixties?' is the wordplay.
I cannot really see how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is present in the answer.
an anagram of 'mail' is 'imal' which is located in the answer.
This may be the basis of the clue (or it may be nonsense).

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I've seen this clue in The Independent.

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