Sailor carts off flan - that's not realistic (8,3)

I believe the answer is:

abstract art

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'not realistic' is the definition.
I can't tell whether this definition defines the answer.

'sailor carts off flan' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'off' is an anagram indicator.
'flan' becomes 'tart' (I've seen this before).
'carts' is an anagram of 'strac'.
'ab'+'strac'+'tart'='ABSTRACT ART'

'that's' is the link.

Can you help me to learn more?

(Another definition for abstract art that I've seen is " Nonrepresentational paintings, sculpture etc".)

I've seen this clue in The Daily Express.

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