Retro party gets essentially best songs (4)
I believe the answer is:
odes
'songs' is the definition.
(I've seen this before)
'retro party gets essentially best' is the wordplay.
'retro' shows that the letters should be reversed in order (retro is Latin for 'backwards').
'party' becomes 'do' (do is a kind of party).
'gets' is a charade indicator (letters next to each other).
'essentially' means to look at the middle letters.
The middle letters of 'best' are 'es'.
'do' written backwards gives 'od'.
'od'+'es'='ODES'
(Other definitions for odes that I've seen before include "To a Skylark, To a Nightingale etc" , "Lyric poems" , "Poems in praise" , "verse" , "Keats was fond of them" .)