Fixed sum given regularly (9)
I believe the answer is:
allowance
'fixed sum given regularly' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for allowance that I've seen before include "Fixed sum given regularly" , "Alloted share" , "Call on with awe for pocket-money or other grant" , "Ration, quota" , "Allotted share" .)