Terror regarding painting technique (7)
I believe the answer is:
impasto
'painting technique' is the definition.
(I've seen this before)
'terror regarding' is the wordplay.
'terror' becomes 'imp'.
'regarding' becomes 'asto'.
'imp'+'asto'='IMPASTO'
(Other definitions for impasto that I've seen before include "Technique of applying paint thickly" , "Method of painting" , "Art technique of laying paint on thickly" , "Slapping paint on" , "Thick painting technique" .)