Maybe Mirror reader backs football's decision- maker (9)
I believe the answer is:
reflector
'maybe mirror' is the definition.
'reader backs football's decision-maker' is the wordplay.
'reader' becomes 'lector' ('lector' can be a synonym of 'reader').
'backs' is a charade indicator (letters next to each other).
'football's decision-maker' becomes 'ref'.
'lector' put after 'ref' is 'REFLECTOR'.
(Other definitions for reflector that I've seen before include "Newton saw through this" , "Mirror (not a good one?)" , "Eg, cat's eye" , "One thinking" , "telescope" .)