A serving icon playing — fourth ace in set? (5,10)

I believe the answer is:

sense impression

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'fourth ace in set?' is the definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Maybe they are linked in a way I don't understand?

'a serving icon playing' is the wordplay.
'a serving icon' becomes 'sense' (I can't explain this - if you can you should give a lot more credence to this answer).
'playing' becomes 'impression' (impression is a kind of playing).
'sense'+'impression'='SENSE IMPRESSION'

Can you help me to learn more?

I've seen this clue in The Guardian.

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