Capital firm keeping tax returns for powerful Roman (7)
I believe the answer is:
octavia
'roman' is the definition.
(I know that Octavia country of citizenship Ancient Rome)
'capital firm keeping tax returns' is the wordplay.
'capital' becomes 'AI' (resembles A1, which can mean capital or excellent).
'firm' becomes 'co' (abbreviation for company).
'keeping' is an insertion indicator (some letters kept inside).
'tax' becomes 'VAT' (UK Value Added Tax).
'returns' is a reversal indicator.
'ai'+'co'='aico'
'aico' going around 'vat' is 'aivatco'.
'aivatco' backwards is 'OCTAVIA'.
'for powerful' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for octavia that I've seen before include "Sister of Augustus" , "tragedy" , "Shakespeare character" , "Antony's wife" , "Wife of Nero" .)