Silent, prepared to pay attention (6)
I believe the answer is:
listen
'pay attention' is the definition.
(to listen to someone)
'silent prepared' is the wordplay.
'prepared' is an anagram indicator.
'silent' is an anagram of 'LISTEN'.
'to' acts as a link.
(Other definitions for listen that I've seen before include "Make an effort to hear" , "Pay heed (to advice)" , "Attend (to a sound)" , "Harken" , "Give one's attention" .)