Brief row about maiden over (5)
I believe the answer is:
remit
'brief' is the definition.
(brief can mean someone's job or remit)
'row about maiden over' is the wordplay.
'row' becomes 'tier' (a tier is a row of things).
'about' indicates putting letters inside.
'maiden' becomes 'm' (cricket abbreviation).
'over' says the letters should be written in reverse.
'tier' enclosing 'm' is 'timer'.
'timer' back-to-front is 'REMIT'.
(Other definitions for remit that I've seen before include "Pay; mail" , "Cancel - terms of reference" , "Task/area assigned (to an organisation)" , "Send payment for timer" , "Shorten sentence or send money" .)