Shrewd account about one of old (7)
I believe the answer is:
archaic
'old' is the definition.
(similar in meaning)
'shrewd account about one' is the wordplay.
'shrewd' becomes 'arch' (I've seen this before).
'account' becomes 'ac' (abbreviation for account).
'about' means one lot of letters goes inside another.
'one' becomes 'I' (Roman numeral).
'ac' going around 'i' is 'aic'.
'arch'+'aic'='ARCHAIC'
'of' is the link.
(Other definitions for archaic that I've seen before include "Of a much earlier period" , "Very old or old-fashioned" , "Extremely old" , "From the past" , "Ancient, no longer current" .)