Listen to them fart endlessly (4)
I believe the answer is:
hear
'listen to' is the definition.
(to hear something is to listen to it)
'them fart endlessly' is the wordplay.
'them' becomes 'he' (I can't explain this - if you can you should believe this answer much more).
'endlessly' means to look at the middle letters (the ends of the words are removed).
The middle letters of 'fart' are 'ar'.
'he'+'ar'='HEAR'
Can you help me to learn more?
(Other definitions for hear that I've seen before include "Perceive aurally" , "attend" , "Get wind of" , "Hark" , "Discover aurally" .)