Attendant always round queen, ready first and last (7)
I believe the answer is:
equerry
'attendant' is the definition.
(I know that equerry is a type of attendant)
'always round queen ready first and last' is the wordplay.
'always' becomes 'eer' (poetic way of saying ever).
'round' is an insertion indicator.
'queen' becomes 'qu' (abbreviation for queen).
'first and last' suggests removing the centre (only the first and last letters are used).
'ready' with its centre taken out is 'ry'.
'eer' enclosing 'qu' is 'equer'.
'equer'+'ry'='EQUERRY'
(Other definitions for equerry that I've seen before include "Sovereign's officer" , "Officer of the British royal household" , "Officer attending a royal family member" , "Attendant in royal household" , "Attendant at palace" .)