Informed where to go quietly (2,3,4)
I believe the answer is:
in the loop
'informed' is the definition.
(in the loop means kept informed)
'where to go quietly' is the wordplay.
'where to go' becomes 'in the loo' (in the toilet).
'quietly' becomes 'p' (p for piano and quiet).
'intheloo'+'p'='IN THE LOOP'
(Other definitions for in the loop that I've seen before include "briefed?" , "kept informed" , "Well informed" .)