Informed about nags (4)
I believe the answer is:
sang
'informed' is the definition.
(I've seen this in other clues)
'about nags' is the wordplay.
'about' indicates an anagram.
'nags' is an anagram of 'SANG'.
(Other definitions for sang that I've seen before include "Chorused" , "Was in a choir" , "Made music with the voice" , "produced a melody" , "Took part in a vocal performance" .)