Award quartet gold book, mostly vulgar (4,7)
I believe the answer is:
ivor novello
'award' is the definition.
I know nothing about this answer so I can't judge whether this works.
'quartet gold book mostly vulgar' is the wordplay.
'quartet' becomes 'IV' (Roman numerals for four).
'gold' becomes 'or' ('or' is the heraldic name for gold).
'book' becomes 'novel' (novel is a kind of book).
'mostly' means to remove the last letter (most but not all of the word).
'vulgar' becomes 'low'.
'low' with its last letter taken away is 'lo'.
'iv'+'or'+'novel'+'lo'='IVOR NOVELLO'
Can you help me to learn more?
(Other definitions for ivor novello that I've seen before include "Welsh actor, composer, singer" , "who composed songs" .)