Enormous, fantastic treat in box (10)

I believe the answer is:

exorbitant

'enormous' is the definition.
(thesaurus)

'fantastic treat in box' is the wordplay.
'fantastic' indicates an anagram.
'treat'+'in'+'box'='treatinbox'
'treatinbox' is an anagram of 'EXORBITANT'.

(Other definitions for exorbitant that I've seen before include "Unreasonable" , "High cost" , "Very dear" , "going beyond the limits?" , "overpriced" .)

I've seen this clue in The Telegraph.

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