Gay piece has garbage prose needing a rewrite (7,5)

'gay piece' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'garbage prose needing a rewrite' is the wordplay.
'garbage' becomes 'beggar' (I am not sure about this - if you are sure you should believe this answer much more).
'needing' says to put letters next to each other.
'rewrite' is an anagram indicator (I've seen 'rewritten' mean this).
'prose' put after 'a' is 'aprose'.
'aprose' with letters rearranged gives 'sopera'.
'beggar'+'sopera'='BEGGARS OPERA'

'has' is the link.

Can you help me to learn more?