Briefly, excuse a bachelor who discovers great riches? (3,4)
I believe the answer is:
ali baba
'who discovers great riches?' is the definition.
'briefly excuse a bachelor' is the wordplay.
'briefly' means to remove the last letter.
'excuse' becomes 'alibi' (I've seen this before).
'bachelor' becomes 'ba' (the qualification: Bachelor of Arts).
'alibi' with its last letter taken off is 'alib'.
'alib'+'a'+'ba'='ALI BABA'
(Other definitions for ali baba that I've seen before include "Hero from Arabian Nights who said ''open sesame''" , "Pantomime character in contention with 40 thieves" , "Arabian Nights hero who opposed forty thieves" , "Pantomine hero opposed to 40 Thieves" , "PANTO (part title)" .)