Maiden about to meet king's brother (4)
I believe the answer is:
monk
'brother' is the definition.
(brother can mean a monk)
'maiden about to meet king's' is the wordplay.
'maiden' becomes 'm' (cricket abbreviation).
'about' becomes 'on' (as in a book 'on' a certain topic).
'to meet' says to put letters next to each other.
'king' becomes 'K' (abbreviation for king in chess).
'm'+'on'+'k'='MONK'
(Other definitions for monk that I've seen before include "Religious brother" , "Man in a religious order" , "Setter" , "Thelonious - - (jazz)" , "One vowed" .)