Are they said to sum up the possibilities of publicity? (5)

I believe the answer is:

admen

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'are they' is the definition.
The definition suggests a plural noun which matches the answer.

'said to sum up the possibilities of publicity?' is the wordplay.
'said' indicates a 'sounds like' (homophone) clue.
'to sum up' becomes 'add' ('add' can be a synonym of 'sum up').
'the possibilities of publicity?' becomes 'men' (I can't justify this - if you can you should believe this answer much more).
'add' is a homophone of 'ad'.
'ad'+'men'='ADMEN'

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I've seen this clue in the Evening Standard.

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