Funny smell starts to occasionally really overpower us (8)
I believe the answer is:
humorous
'funny' is the definition.
(similar in meaning)
'smell starts to occasionally really overpower us' is the wordplay.
'smell' becomes 'hum' (something with a bad smell is 'humming').
'starts to' indicates taking the first letters.
The initial letters of 'occasionally really overpower' is 'oro'.
'hum'+'oro'+'us'='HUMOROUS'
(Other definitions for humorous that I've seen before include "Risible" , "Comic" , "Funny, amusing" , "Causing amusement" , "Droll, witty" .)