Previously a nobleman to current queen (7)
I believe the answer is:
earlier
'previously' is the definition.
(synonyms)
'a nobleman to current queen' is the wordplay.
'a nobleman' becomes 'earl' (earl is a kind of nobleman).
'to current' becomes 'I' (symbol for electric current).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'earl'+'i'+'er'='EARLIER'
(Other definitions for earlier that I've seen before include "(Happening) before in time" , "Prior" , "Formerly" , "at a previous date" , "At a previous time" .)