Advance requirement in front of Her Majesty has to be acceptable (4,6)
I believe the answer is:
pass muster
'to be acceptable' is the definition.
(to pass muster is to be good enough)
'advance requirement in front of her majesty' is the wordplay.
'advance' becomes 'pass' (passing is a kind of advancing).
'requirement' becomes 'must' (I've seen this in another clue).
'in front of' says to put letters next to each other (some letters go in front of others).
'her majesty' becomes 'ER' (Elizabeth Regina).
'pass'+'must'+'er'='PASS MUSTER'
'has' acts as a link.
(Other definitions for pass muster that I've seen before include "To fit the bill" , "Be good enough" , "appear acceptable" , "Satisfy, suffice" .)