Painting regularly turned, we suspect (4)
I believe the answer is:
nude
'painting' is the definition.
(nude is a kind of painting)
'regularly turned we suspect' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'suspect' indicates an anagram.
'turned'+'we'='turnedwe'
The alternating letters of 'turnedwe' are 'unde'.
'unde' is an anagram of 'NUDE'.
(Other definitions for nude that I've seen before include "Naked, bare" , "Classic art subject" , "Undressed" , "being out of the habit?" , "The Thinker, maybe" .)