A cheap mongrel managed a brainy image (13)

I believe the answer is:

encephalogram

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'a brainy image' is the definition.
The definition suggests a singular noun which matches the answer.

'a cheap mongrel managed' is the wordplay.
'managed' indicates anagramming the letters.
'a'+'cheap'+'mongrel'='acheapmongrel'
'acheapmongrel' with letters rearranged gives 'ENCEPHALOGRAM'.

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I've seen this clue in The Daily Express.

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