Bendy buses can't matter (9)
I believe the answer is:
substance
'matter' is the definition.
('substance' can be a synonym of 'matter')
'bendy buses can't' is the wordplay.
'bendy' indicates an anagram (the word is bent out of shape).
'buses'+'cant'='busescant'
'busescant' with letters rearranged gives 'SUBSTANCE'.
(Other definitions for substance that I've seen before include "power" , "Matter or material that a thing is made of" , "Physical material" , "wealth" , "Property" .)