Substance agency has in mind (5)
I believe the answer is:
means
I believe this is a triple definition!
'substance' is the first definition.
(I know that substance can be written as means)
'agency' is the second definition.
(I've seen this in another clue)
'has in mind' is the third definition.
('mean' can be a synonym of 'have in mind')
(Other definitions for means that I've seen before include "Medium used to achieve a result" , "With which an end is achieved" , "Designs" , "Signifies" , "considerable income" .)