It's a dour play for those listening in
I believe the answer is:
auditors
'those listening in' is the definition.
I can't judge whether this defines the answer.
'it's a dour play' is the wordplay.
'play' indicates an anagram.
'its'+'a'+'dour'='itsadour'
'itsadour' with letters rearranged gives 'AUDITORS'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for auditors that I've seen before include "They check the accounts annually" , "checkers - with 12a" .)