Queen in two types of gold: a wondrous sight at night (6)
I believe the answer is:
aurora
'wondrous sight at night' is the definition.
I can't tell whether this defines the answer.
'queen in two types of gold a' is the wordplay.
'queen' becomes 'r' (r is abbreviation regina. e.g. in ER ).
'in' indicates putting letters inside.
'two types of' becomes 'au' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'gold' becomes 'or' ('or' is the heraldic name for gold).
'au'+'or'='auor'
'r' placed inside 'auor' is 'auror'.
'auror'+'a'='AURORA'
Can you help me to learn more?
(Other definitions for aurora that I've seen before include "Phenomenon in sky" , "Nature's 11 in the Arctic" , "Coloured light in the sky" , "Roman goodess of the dawn" , "dawn arrives" .)