Notes about masonry (5)
I believe the answer is:
stone
'masonry' is the definition.
(I've seen this in another clue)
'notes about' is the wordplay.
'about' is an anagram indicator.
'notes' with letters rearranged gives 'STONE'.
(Other definitions for stone that I've seen before include "Boulder" , "Rock; hard seed" , "Gem; Staffs. town" , "See 1" , "Piece of rock - weight" .)