Vicious, silent, evil bugs (7,2)
I believe the answer is:
listens in
'bugs' is the definition.
The definition and answer can be both to do with perception as well as being verbs in their -s form.
Maybe they are linked in a way I don't understand?
'vicious silent evil' is the wordplay.
'vicious' indicates anagramming the letters.
'evil' becomes 'sin' (synonyms).
'silent' with letters rearranged gives 'listen'.
'listen'+'sin'='LISTENS IN'
Can you help me to learn more?
(Other definitions for listens in that I've seen before include "earwigs" , "Intercepts messages" .)