Listened (5,2)
There are a few possibilities for this:
tuned in
'listened' is the definition.
(attending is a kind of listening)
This is the entire clue.
(Other definitions for attended that I've seen before include "'Went to, was present at (8)'" , "Was present at or waited upon" , "Paid heed" .)
(Other definitions for tuned in that I've seen before include "Prepared to hear" , "Adjusted radio set" .)