What's ideal for nice pet is being spoiled (10)
I believe the answer is:
perfection
'what's ideal' is the definition.
(perfection is a kind of ideal)
'for nice pet is being spoiled' is the wordplay.
'is being spoiled' indicates anagramming the letters.
'for'+'nice'+'pet'='fornicepet'
'fornicepet' is an anagram of 'PERFECTION'.
(Other definitions for perfection that I've seen before include "Highest state" , "Faultlessness" .)