Masterly advert for a new pet (5)

I believe the answer is:

adept

'masterly' is the definition.
(thesaurus)

'advert for a new pet' is the wordplay.
'advert' becomes 'ad' (synonyms).
'for' means one lot of letters go next to another.
'a new' indicates an anagram.
'pet' is an anagram of 'ept'.
'ad'+'ept'='ADEPT'

(Other definitions for adept that I've seen before include "Handy" , "efficient" , "Skilful and adroit" , "Highly proficient" , "skilled performer" .)

I've seen this clue in the Evening Standard.

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