Noisy fool leaves lesson in love (9)
I believe the answer is:
clamorous
'noisy' is the definition.
(similar in meaning)
'fool leaves lesson in love' is the wordplay.
'fool' becomes 'ass' (both can mean a stupid person).
'leaves' suggests deleting specific letters.
'lesson' becomes 'class' (synonyms).
'in love' becomes 'amorous' (I've seen this before).
'class' with 'ass' taken out is 'cl'.
'cl'+'amorous'='CLAMOROUS'
(Other definitions for clamorous that I've seen before include "Insist" , "Confusedly noisy" , "vociferous" .)