Engraving that is inspired by last of Jackson Pollock's three pivotal pieces (6)
I believe the answer is:
niello
'engraving' is the definition.
(I've seen this before)
'that is inspired by last of jackson pollock's three pivotal pieces' is the wordplay.
I cannot really understand how this works, but
'of' could be 'o' and 'o' is present in the answer.
'that is' could be 'ie' ('i.e.' can be a synonym of 'that is') and 'ie' is located in the answer.
This explanation may well be incorrect...
(Other definitions for niello that I've seen before include "Method of engraving" , "Style of ornamenting metal, lo line (anag.)" , "Black filling for engravings on metal; lo line (anag.)" .)