I'm thinking this is a mnemonic device for remembering how to:
Spell the offspring of a swan, i.e. a CYGNET.
'Empty' here is a cryptic-esque way of instructing one to take only the first and last letters of the words that follow (thereby removing their contents, or emptying them), i.e. 'Empty City, Green' emphasises the letters CYGN.
Next, the mnemonic creator holds a strong association between the word 'Dwarfs' and the letters ET. This is possibly because the title character in the classic 1982 Steven Spielberg movie E.T. The Extra-Terrestrial is a short character played by three different actors, two of whom had dwarfism.
(Alternatively, 'Empty' only links to 'City', providing CY; 'Green' indicates only its single-letter abbreviation G; and in the Snow White tale there were only seven dwarfs - not ten, thinks the mnemonic creator - and so translates 'not ten' as 'the opposite of ten', i.e. 'TEN backwards' or NET...)
As for the title?
The Tchaikovsky ballet Swan Lake was originally a flop after its premiere in Moscow in 1877. However, it was revived in St Petersburg, performed for the first time in this new run on 15 January 1895 at the Mariinsky Theatre, after which it soared in popularity, becoming one of the most popular and well-known ballets worldwide. This year marks the 125th anniversary of the revival - a landmark the OP thought worthy of commemorating in this puzzle :)
Personally, however, if I were coming up with a mnemonic for 'CYGNET' (yes, I realise you weren't asking), this following one is my favourite simple acrostic of all the ones that flew round my mind overnight... It makes use of the male swan being known as a 'cob', the swan being renowned for its temper, and the famous ballet:
Cob's Young Gets Nasty - Eats Tchaikovsky!
(Feel free to start using it yourself!)