Cheaper test turned out to be favourite (8,3)

I believe the answer is:

teachers pet

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'to be favourite' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'cheaper test turned' is the wordplay.
'turned' indicates an anagram.
'cheaper'+'test'='cheapertest'
'cheapertest' with letters rearranged gives 'TEACHERS PET'.

'out' is the link.

Can you help me to learn more?

(Other definitions for teachers pet that I've seen before include "Favourite in form" , "Class favourite" , "goody-goody" , "Favoured child at school" , "Subject of favouritism at school" .)

I've seen this clue in The Mirror.

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