Bleating about material (8)
I believe the answer is:
tangible
'material' is the definition.
(similar in meaning)
'bleating about' is the wordplay.
'about' is an anagram indicator.
'bleating' is an anagram of 'TANGIBLE'.
(Other definitions for tangible that I've seen before include "Able to be perceived by touch" , "Material" , "Palpable" , "Concrete - bleating (anag)" , "Having real substance" .)