Called about what is to replace picture (6)
I believe the answer is:
rehang
'to replace picture' is the definition.
(to hang a picture in a different place)
'called about what' is the wordplay.
'called' becomes 'rang' ('ring' can be a synonym of 'call').
'about' means one lot of letters goes inside another.
'what' becomes 'eh' (I've seen this in other clues).
'rang' enclosing 'eh' is 'REHANG'.
'is' acts as a link.
(Other definitions for rehang that I've seen before include "Suspend once more" , "Move of pictures in a gallery" , "Give further showing of picture" , "Put up once more" , "demonstrate initial failure of capital punishment?" .)