Precision casting icy net (6)
I believe the answer is:
nicety
'precision' is the definition.
(I've seen this before)
'casting icy net' is the wordplay.
'casting' indicates an anagram.
'icy'+'net'='icynet'
'icynet' with letters rearranged gives 'NICETY'.
(Other definitions for nicety that I've seen before include "Refinement" , "Delicacy" , "shade?" , "Fine distinction" , "Subtle difference" .)