Sign discovered in form of Maori art (7)
I believe the answer is:
origami
'art' is the definition.
(I've seen this before)
'sign discovered in form of maori' is the wordplay.
'discovered' indicates the central letters.
'in' is an insertion indicator.
'form of' is an anagram indicator (the letters need to be in another 'form').
The central letters of 'sign' are 'ig'.
'maori' with letters rearranged gives 'orami'.
'ig' placed within 'orami' is 'ORIGAMI'.
(Other definitions for origami that I've seen before include "It's crafty folding" , "Art originally created in simple materials to design bird forms" , "Paperwork, as it were" , "Japanese paper-folding art" , "Japanese craft of paper-tearing" .)