Artfully hide returning fat with particular angle (8)
I believe the answer is:
dihedral
'with particular angle' is the definition.
'artfully hide returning fat' is the wordplay.
'artfully' indicates anagramming the letters.
'returning' shows that the letters should be reversed in order.
'fat' becomes 'lard' (I've seen this before).
'lard' back-to-front is 'dral'.
'hide' is an anagram of 'dihe'.
'dihe'+'dral'='DIHEDRAL'
(Other definitions for dihedral that I've seen before include "Two-faced" , "Upward inclination of a plane's wings" , "surrounded by a couple of planes" , "angle" .)