You must have passed this and they say you'll be accepted (5)
I believe the answer is:
urine
'this and they say you'll be accepted' is the definition.
The definition suggests a singular noun which matches the answer.
'you must have passed' is the wordplay.
'you' becomes 'u' (homophones).
'must have' means one lot of letters go next to another.
'passed' becomes 'rine' (I can't explain this - if you can you should believe this answer much more).
'u'+'rine'='URINE'
Can you help me to learn more?
(Other definitions for urine that I've seen before include "Stuff that's passed" , "Water that one passes" , "Waste product" , "Wee" .)