Hate new painting, basically (2,5)
I believe the answer is:
at heart
'basically' is the definition.
(both can mean fundamentally or deep down)
'hate new painting' is the wordplay.
'new' indicates anagramming the letters.
'painting' becomes 'art' (painting is an art).
'hate' anagrammed gives 'athe'.
'athe'+'art'='AT HEART'
(Other definitions for at heart that I've seen before include "real character" , "In essence" , "In one's innermost feelings, in that era" , "Essentially" , "Basically" .)