Noble American maiden lady, rather old (7)

I believe the answer is:
grandam
'lady rather old' is the definition.
I can't tell whether this definition defines the answer.
'noble american maiden' is the wordplay.
'noble' becomes 'grand' (similar in meaning).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'maiden' becomes 'm' (cricket abbreviation).
'grand'+'a'+'m'='GRANDAM'
Can you help me to learn more?
(Another definition for grandam that I've seen is " Experienced old woman".)
