Druh6sm-
1a is a very dense clue.
Definition is 'provides illumination in a museum' although 'illumination' is a misdirection. Think less light source and more knowledge sharing.
Parses 2,5,3, though the 3 is inserted ('invested') into the 5 letter word.
First three words provides letters for the 3.
Gold gives the opening 2 letters.
The 5 is a word in the clue itself