Nymph heard near middle of meadow (5)
I believe the answer is:
naiad
This clue could be a double definition.
'nymph' is the first definition.
(naiad is a kind of nymph)
'heard near middle of meadow' is the second definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
(Other definitions for naiad that I've seen before include "Greek mythological water nymph" , "watery spirit" , "Classic spirit" , "Fabulous spring being" , "Aquatic larva of a dragonfly" .)