Bitter account by leading royal writer (7)
I believe the answer is:
acerbic
'bitter' is the definition.
(synonyms)
'account by leading royal writer' is the wordplay.
'account' becomes 'ac' (abbreviation for account).
'by' says to put letters next to each other.
'leading' is a charade indicator (letters next to each other).
'royal' becomes 'er' (abbreviation for Elizabeth Regina).
'writer' becomes 'bic' (kind of pen).
'ac'+'er'+'bic'='ACERBIC'
(Other definitions for acerbic that I've seen before include "Acrimonious" , "Bitter-tasting" , "Harsh and sharp in speech" , "Sour; sharp" , "Sour in taste or harsh in tone" .)